Why does this question make me laugh?
I think I mostly agree with Doris and Bug -- they probably are generally complainers, however, I agree with the point someone brought up that being alone with kids all the time can tend to make one vent a lot when finally in adult company.
When I was a SAHM of little kids, I never got a break from them, and I used to think I got what I called "verbal diarrhea" when in the company of adults. It wasn't all complaining though, just the release of finally being in the company of people I could really talk to. Kids are cute, but little ones aren't generally scintillating conversationalists.
Despite Mum4ever's experience, one of the only ways I could endure the teen years was to be able to vent about them to friends. Thankfully after 10 years of it among 3 kids, it's almost over. Now if I had had a supportive, united husband throughout the experience, instead of one who undermined me, it would have been a lot more brief. Whatever.
Mira -- hilarious response!