I used to work as an adcomm at a b-school and I can tell you adcomms do discuss apps with other adcomms/schools. Though it's not usually done in an identifying way (Joe Blow submitted the dumbest app, for instance, is rarely actually stated), comments such as, "I reviewed the craziest app the other day. This app submitted a personal statement about how he 'gave birth' to a landscaping business. Just the way he put it made me laugh." or "I actually read a PS in which the app said he was only applying because his daddy made him and was an alum!"
I've no doubt adcomms share stories, and if you're submitting to more than one school, they'll usually find out.