I absolutely love meeting people from the forum... so far, I haven't had a bad experience, though I also don't meet anyone who is single and of the opposite sex either, without my wife also meeting and knowing them. History has brought me stalkers from this forum... so I am cautious at first.
All relationships evolve. The ones I have seen go nasty and had to get involved in from a forum perspective, typically involved one person becoming dependent upon the other, yet the other had just as much fault by not securing more stricter boundaries right from start, because they thought they were helping the person by being a friend. All very noble, honest and well, though the end result is still typically the same, with the person thinking they can help someone eventually becoming drained, depressed and dragged down by the dependent person.
The dependent person then resents the apparent friend because they begin to ignore their calls, not answer the phone, email, etc... so the dependent person ramps up, panics and tries communicating more, further scaring the person away.
When eventually the helper of the friendship stands their ground and puts boundaries up, the dependent person has already become dependent, thus now they become stalkerish / aggressive to the other, all because these boundaries weren't put up right from the start.
Usually, both people are at fault under such situations. One though due to nobility, courtesy, thinking they are helping the person, the other to becoming co-dependent upon another due to selfish desires.
Funnily, both do it unknowingly the majority of the time.
So if you know about these things prior, then you can factor in your safety before hand, even when you get to know the person, maintain boundaries and honesty with the person at all times. If something changes, tell them. If you need time-out for a week, two, etc, tell them. Set boundaries for contact once or twice a week, nothing more... if not further apart, as friendships with depression involved can do serious damage if you talk too often.