Why do I keep hearing this line that the comic had written itself into a corner with MJ? There's almost too many solutions, not the least of which is a simple break-up; their relationship was in constant jeopardy anyway, and it wouldn't be the first girl Spider-Man broke up with who was aware of his secret identity. And that's assuming that it's even a problem; even if Mary Jane had never existed (ha), Spider-Man would still have loved ones to protect by maintaining his cover. And even if you're just averse to Peter's monogamy, you can't deny that it's a natural extension of the premise, and that it really should work. In fact, I can think of at least one instance of it being imitated (ever seen Batman Beyond?).