As a result of an injury sustained during battle, Spider-Man faints at the end of #64 and gets taken to jail. It’s seems a little weird–it’s just his arm, and he’s certainly taken bigger beatings–but I think it’s explainable by the fact that Peter takes his personal life waaaaaay too seriously. He’s all stressed about Gwen and Captain Stacy and his Aunt (who is also fainting quite a bit). Gwen thinks Peter should move out of Aunt May’s house because she’s smothering him, and Aunt May agrees (kind of), so the ladies are really working him over. So maybe all of that put together explains why he passes out.
It also makes for a really neat prison break story.