I have dated two former sp's. The first we were both quite young, and never moved in with each other or anything serious. She told me about her "past" within the first two weeks, and she cried after telling me. I told her I didn't care and I really didn't, she was with me at that time and screw everything else (we were young lol). We live in different places now, and still keep in touch once or twice a year. She has told me several devastating stories of breakups with "Mr.Right" after she discloses to them about her past...15 years ago. I can really feel for sp's who have to try and jump this hurdle, the best I can ever come up with for her is that they were never Mr. Right, but ya kinda seems hollow sometimes.
The other, well it's interesting to get told such things after being together for a few years lol! It never really left us, not that she did it, but that she held back for so long. And i'm not sure if she ever really trusted me when I told her I was %100 ok with her past, and really not ok at all with her feeling like she had something to hide, like I would be ashamed of her or something. I used to think that lack of trust destroyed the relationship, whereas now I think I never really had hers.
Funny thing is I didn't try out "the hobby" until after these events and getting single. Now that I have I wonder how it will go down when I disclose these activities to a new partner whom i'm very serious about. Funny how you can only really understand some things after doing them yourself.