Gambit openings are usually based on sacrificing pieces to have much better piece development.
Some gambits, like Queen's gambit, or King's gambit, I can understand the idea. However, I cannot evaluate Danish gambit. White sacrifices two pawns, has two developed bishops, but Black seems to be able to cover up pretty fast.
[fen ""] 1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 cxb2 5. Bxb2
Although it is obvious that Black has no piece development, how can White play to take advantage of it?