Not too long ago, someone contacted me (or I contacted them... can't remember) on OKCupid. We exchanged email, and then phone numbers, and it seemed like we were getting to know each other well enough to meet.
So, he sends me a message that his girlfriend (I didn't know he had one... and it gives me pause that adults call someone they're involved with a" girlfriend", but anyhow...) might not be able to visit him that weekend because of her husband suddenly deciding he might not be comfortable with the situation. Mr. Last Minute then invited me to visit, as he was home with no car (his wife and kids were away for the weekend), and a halfway meet was out of the question.
I wrote back that I might be able to visit on X day, but I would have to synchronize my swimming with my partner. While I was in the process of checking, I get an email stating that Mr. Last Minute "needs this time to get his head together". He doesn't mention that he's invited me, or apologize for changing his mind at the last minute. He also states that he will write in full soon.
Soon has now become late. At this point, I'm not interested. This has made me think that if I'm going to meet someone at their home, and they are married or otherwise committed to someone, I want to meet their spouse/partner first.
So... what are your dealbreakers?