user24210: Let's say I play only e4/e5 (but this question might also come up on d4/d5). If I was a beginner - unaware of opening theory - but could count at least 3 moves ahead, could I survive (=not be lost at move 15) basically any type of opening by following only the basic "principles" ?
I am asking because if I wanted to teach somebody openings, I should obviously just first teach them principles, but what about these opening traps?
I cannot remember one off the top of my head, but I believe there are some openings which look okay, but it turns out there is a forced loss after 10 moves.

user15223: Sometimes violating opening principles is one's best way of playing for an advantage. Even if you are not the one playing for advantage, opponent might be.
The first opening that comes to mind is the Two Knights Defense:
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 {Black's played completely according to principles so far - "develop knights before bishops", etc.} 4. Ng5!? {This is White's best way of playing for an advantage, but it violates the opening principle of not moving the same piece twice.} d5 {It's either this or 4...Bc5 giving up the f7-pawn, which is an even riskier move.} 5. exd5 Nxd5?! {This move is known to be dubious, but the main line 5...Na5 is effectively a pawn sacrifice.} 6. d4

With a powerful initiative. White doesn't have a forced win, but has open lines and is ready to castle, with threats such as Qf3 hitting both the d5-knight and f7-pawn.
A different line of the Giuoco Piano comes to mind as well.
[FEN ""]    
  1. e4             e5            
  2. Nf3            Nc6            
  3. Bc4            Bc5           
  4. c3             Nf6          
  5. d4             exd4
  6. e5

Black's best move is 6...d5 (the alternatives are nearly losing), which is not an obvious move and not something that you can find knowing only opening principles.

user17425: In my first 10 years of playing chess I never studied openings.  I studied middle game, positional play, and endings.  Falling for traps is a great way to learn about them, very memorable.  I did play through many master games and so had a feel of openings from that.
Against strong opposition I often ended up in cramped positions struggling for activity out of the opening.  I enjoyed these positions.  Korchnoi was my hero :)
Eventually I didn't like those positions and then I learned openings.
I have no regrets.

user4418: 
I am asking because if I wanted to teach somebody openings, I should obviously just first teach them principles, but what about these opening traps?

Exactly. There are many opening traps and if you don't know them they are very easy to fall into. For instance it is easy for a beginner playing the Ruy Lopez to fall for a trap which is so old it is called the "Noah's Ark" trap:
[fen ""]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 d6 5. d4  b5 6. Bb3 Nxd4 7. Nxd4 exd4 8. Qxd4?? c5 9. Qd5 Be6 10. Qc6+ Bd7 11. Qd5 c4

You either learn this stuff or risk becoming a victim.

24210: <p>Let's say I play only e4/e5 (but this question might also come up on d4/d5). If I was a beginner - unaware of opening theory - but could count at least 3 moves ahead, could I survive (=not be lost at move 15) basically any type of opening by following only the basic &quot;principles&quot; ?</p>
<p>I am asking because if I wanted to teach somebody openings, I should obviously just first teach them principles, but what about these opening traps?</p>
<p>I cannot remember one off the top of my head, but I believe there are some openings which look okay, but it turns out there is a forced loss after 10 moves.</p>
 15223: <p>Sometimes violating opening principles is one's best way of playing for an advantage. Even if you are not the one playing for advantage, opponent might be.</p>
<p>The first opening that comes to mind is the Two Knights Defense:</p>
<pre><code>[FEN &quot;rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1&quot;]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 {Black's played completely according to principles so far - &quot;develop knights before bishops&quot;, etc.} 4. Ng5!? {This is White's best way of playing for an advantage, but it violates the opening principle of not moving the same piece twice.} d5 {It's either this or 4...Bc5 giving up the f7-pawn, which is an even riskier move.} 5. exd5 Nxd5?! {This move is known to be dubious, but the main line 5...Na5 is effectively a pawn sacrifice.} 6. d4
</code></pre>
<p>With a powerful initiative. White doesn't have a forced win, but has open lines and is ready to castle, with threats such as Qf3 hitting both the d5-knight and f7-pawn.</p>
<p>A <a href="https://chess.stackexchange.com/questions/19967/the-giuoco-piano-after-4-c3-nf6-5-d4-exd4-6-e5">different line</a> of the Giuoco Piano comes to mind as well.</p>
<pre><code>[FEN &quot;&quot;]    
  1. e4             e5            
  2. Nf3            Nc6            
  3. Bc4            Bc5           
  4. c3             Nf6          
  5. d4             exd4
  6. e5
</code></pre>
<p>Black's best move is 6...d5 (the alternatives are nearly losing), which is not an obvious move and not something that you can find knowing only opening principles.</p>
 17425: <p>In my first 10 years of playing chess I never studied openings.  I studied middle game, positional play, and endings.  Falling for traps is a great way to learn about them, very memorable.  I did play through many master games and so had a feel of openings from that.</p>
<p>Against strong opposition I often ended up in cramped positions struggling for activity out of the opening.  I enjoyed these positions.  Korchnoi was my hero :)</p>
<p>Eventually I didn't like those positions and then I learned openings.</p>
<p>I have no regrets.</p>
 4418: <blockquote>
<p>I am asking because if I wanted to teach somebody openings, I should obviously just first teach them principles, but what about these opening traps?</p>
</blockquote>
<p>Exactly. There are many opening traps and if you don't know them they are very easy to fall into. For instance it is easy for a beginner playing the Ruy Lopez to fall for a trap which is so old it is called the &quot;Noah's Ark&quot; trap:</p>
<pre><code>[fen &quot;&quot;]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 d6 5. d4  b5 6. Bb3 Nxd4 7. Nxd4 exd4 8. Qxd4?? c5 9. Qd5 Be6 10. Qc6+ Bd7 11. Qd5 c4
</code></pre>
<p>You either learn this stuff or risk becoming a victim.</p>
