From what I have seen, the problem reaches crazy proportions amongst gay men, presumably due to the easier availability of casual sex - a boyfriend of a close friend of mine had apparently slept with over 1000 people, which blew my head off (no double meaning at all intended) when my friend told me. Now THAT'S self-destructive behaviour...
1000! A guy at work has confided that he's had over 600 sexual partners in the space of about 6 years. Although he's now happily and monogamously civil partnered for over 8 years (EDIT: obv CPed when it became legal). I guess those sexual encounters were 'healthy' in the way that they didn't affect his ability to love one person.
with the net it's extremely easy to get nookie. Just put in your postcode and you're off...