I haven't ever passed on meeting someone because of another lady they've seen, but I will decline contacting some ladies for references based on previous bad experiences interacting with them. Most ladies are super friendly and helpful, but there are a few who are ... well, not so much.
Like others in this thread, I have skipped meeting people because of a seemingly negative attitude in posting or tendency toward unsafe activities. That's hard to quantify though -- it's not black & white -- and comes down to a gut feeling of concerns over compatibility more than anything. I'm not going to meet someone if I think one or both of us is going to end up disappointed. Let's just save us both the time and trouble, yanno?
On the other hand, board posts and well-written reviews can definitely work FOR someone, too! I get a new board crush like every other week.