I seem to be running into them as well... .one in college years ago was definitely a BPD and I suspect that my ex wife had SOME kind of PD.
I have been online dating since my b/u from my BPDfiance several months ago. I am beginning to feel that the dating sites are places where the overwhelming majority of people are there because there have SOMETHING that makes it difficult to meet people in the first place and/or impossible to sustain a relationship. Kind of like a revolving door of romance for people that have issues that are not resolved.
To that end, the one that I have been dating for the past month or so made it through my 'filters'. We have had some nice times so far but I have not wanted to take it very seriously with her, something bothered me about her but I could not quite put my finger on it (besides her love bombing). I came to find out that she is diagnosed OCD and has periodic episodes. Meanwhile, she has a highly tumultuous relationship with her roommate who fits ALL of the diagnostic criteria for BPD. While she lives there for low rent, she has a decent job and could afford a place of her own if she wanted but she can't leave because the roommate 'needs her'. In response, she works 60-70 hours a week so that she can avoid her!
I have thought about this critically and have tried to identify what kind of signals that I have been sending out that would have attracted this person. The biggest criteria that I have for a romantic interest is that she is educated and can maintain at least a basic conversation (I'm pretty picky huh?). In the end I just think that its the luck of the draw and that online dating is full of these types - almost by definition.
Time to reconstruct my filters.