user15478: The line may seem suspicious at first, but after a few precise moves (some may say artificial moves) by Black an interesting middlegame position is reached.
I did some analysis on my own and probably the strongest line for White is the early Bb5 line, but even there an interesting, unbalanced game arises.
From my analysis, Black eventually reaches equality (at least practically). I use "!" to mark moves that make the variation work.
[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. d3 d5!? 5. exd5 Nxd5 6. O-O Nb6! {Not an excellent move, but a key move for the variation. Now the Queen does not have to defend the knight and is allowed to go to e7} 7. Bb3 {This natural move is the most played} (7. Bb5 {Is the critical continuation. White is pressuring e5} Bd6 8. Bxc6+ {Eliminating the defender first is the most precise way to win the pawn on e5} (8. Nxe5 Bxe5 9. Re1 {This plan does not win a pawn} O-O 10. Bxc6 Bxh2+ 11. Kxh2 Qd6+ 12. Kg1 Qxc6)(8. Re1 f6 9. d4 O-O 10. dxe5 Nxe5 11. Nxe5 fxe5 12. Nc3 Bf5 13. Ne4 Bb4 14. c3 Qxd1 15. Rxd1 Be7 16. Re1 Rad8) 8... bxc6 9. Nxe5 Bxe5 10. Re1 {This line requires some artificial solution from Black} Qe7 11. f4 Bd4+ 12. Kh1 Be6 13. f5 O-O 14. fxe6 Nd5) 7... Bg4! {Indirectly defending e5, disallowing Ng5 and paving the road for long castle by Black} 8. h3 Bh5 9. Re1 Qe7! {This move looks rather artificial but it protects e5 and allows the king to leave the center, which is under pressure} 10. a4 (10. Qe2 f6) {Forcing ...a5 is beneficial to White, as it weakens Black's king shelter} (10. c3 {The game takes similar shape without a4 a5 interposed} O-O-O 11. d4 f6 12. Nbd2 g5 13. Nf1 Kb8 14. Ng3 Bg6) 10... a5 11. Nc3 (11. Be3 O-O-O 12. Bxb6 cxb6 13. Nc3 Kb8 14. Nb5 f5) O-O-O 12. Nb5 Kb8 13. Qe2 f6 14. c3 g5 15. d4 {Practically a totally equal position}

Is there something I am missing? Is Black hopeless at the end of some of the lines?

user28146: There are probably several ways of obtaining an advantage but the most convincing one I can come up with is this:
[fen "r1bqkb1r/ppp2ppp/1nn5/4p3/2B5/3P1N2/PPP2PPP/RNBQ1RK1 w kq - 2 7"]

7.Bb5 Bd6 8.Bxc6+ bxc6 9.Nxe5 Bxe5 10.Re1 Qe7 (10...f6 11.d4 O-O 12.dxe5 Qxd1 13.Rxd1 fxe5) 11.Kh1 O-O 12.f4 f6 13.fxe5 fxe5 14.Be3

In the position after 10.Re1, Stockfish 14 NNUE gives +0.8 at depth 41. That's a great opening advantage and the final position seems fairly miserable for black because of the bad pawn structure.
Some comments have focused on the earlier 8.Re1 variation. Maybe that's because there are a couple of games in the database that have continued like that. I'm sure that variation gives an advantage for white as well, but I don't think one should give much value on non-prepared GM moves.

15478: <p>The line may seem suspicious at first, but after a few precise moves (some may say artificial moves) by Black an interesting middlegame position is reached.</p>
<p>I did some analysis on my own and probably the strongest line for White is the early Bb5 line, but even there an interesting, unbalanced game arises.</p>
<p>From my analysis, Black eventually reaches equality (at least practically). I use &quot;!&quot; to mark moves that make the variation work.</p>
<pre><code>[FEN &quot;&quot;]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. d3 d5!? 5. exd5 Nxd5 6. O-O Nb6! {Not an excellent move, but a key move for the variation. Now the Queen does not have to defend the knight and is allowed to go to e7} 7. Bb3 {This natural move is the most played} (7. Bb5 {Is the critical continuation. White is pressuring e5} Bd6 8. Bxc6+ {Eliminating the defender first is the most precise way to win the pawn on e5} (8. Nxe5 Bxe5 9. Re1 {This plan does not win a pawn} O-O 10. Bxc6 Bxh2+ 11. Kxh2 Qd6+ 12. Kg1 Qxc6)(8. Re1 f6 9. d4 O-O 10. dxe5 Nxe5 11. Nxe5 fxe5 12. Nc3 Bf5 13. Ne4 Bb4 14. c3 Qxd1 15. Rxd1 Be7 16. Re1 Rad8) 8... bxc6 9. Nxe5 Bxe5 10. Re1 {This line requires some artificial solution from Black} Qe7 11. f4 Bd4+ 12. Kh1 Be6 13. f5 O-O 14. fxe6 Nd5) 7... Bg4! {Indirectly defending e5, disallowing Ng5 and paving the road for long castle by Black} 8. h3 Bh5 9. Re1 Qe7! {This move looks rather artificial but it protects e5 and allows the king to leave the center, which is under pressure} 10. a4 (10. Qe2 f6) {Forcing ...a5 is beneficial to White, as it weakens Black's king shelter} (10. c3 {The game takes similar shape without a4 a5 interposed} O-O-O 11. d4 f6 12. Nbd2 g5 13. Nf1 Kb8 14. Ng3 Bg6) 10... a5 11. Nc3 (11. Be3 O-O-O 12. Bxb6 cxb6 13. Nc3 Kb8 14. Nb5 f5) O-O-O 12. Nb5 Kb8 13. Qe2 f6 14. c3 g5 15. d4 {Practically a totally equal position}
</code></pre>
<p>Is there something I am missing? Is Black hopeless at the end of some of the lines?</p>
 28146: <p>There are probably several ways of obtaining an advantage but the most convincing one I can come up with is this:</p>
<pre><code>[fen &quot;r1bqkb1r/ppp2ppp/1nn5/4p3/2B5/3P1N2/PPP2PPP/RNBQ1RK1 w kq - 2 7&quot;]

7.Bb5 Bd6 8.Bxc6+ bxc6 9.Nxe5 Bxe5 10.Re1 Qe7 (10...f6 11.d4 O-O 12.dxe5 Qxd1 13.Rxd1 fxe5) 11.Kh1 O-O 12.f4 f6 13.fxe5 fxe5 14.Be3
</code></pre>
<p>In the position after 10.Re1, Stockfish 14 NNUE gives +0.8 at depth 41. That's a great opening advantage and the final position seems fairly miserable for black because of the bad pawn structure.</p>
<p>Some comments have focused on the earlier 8.Re1 variation. Maybe that's because there are a couple of games in the database that have continued like that. I'm sure that variation gives an advantage for white as well, but I don't think one should give much value on non-prepared GM moves.</p>
