Fried Liver Attack Confuses Computer
I wonder what it says after 6. d4.
FCO doesn't even consider 5...Nxe5, noting that as long ago as 1600 it was know to give White a good attack.
FCO recommends 5...Na5 and notes that 5...Nd4 and 5...b5 have their followers. Stockfish 8, set to 20 ply, recommends 5...Na5 (+0.16: White is effectively 0.16 pawn ahead, basically even), then 5...Nb4 (+0.54), 5...b5 (+0.63) 5...Nd4 (+0.99) 5...Nxd5 (+1.37).
There are those who believe they can get enough developmental compensation for the loss of a pawn. There are those who play 3...h6, the Anti-Friend Liver Defense and others go into the standard Italian Game with 3...Bc4 to prevent Ng5.
I've played the Giuoco Piano and like seeing 3...h6 because it helps me develop with an extra tempo.