Apparently quite a few people still visiting my site to investigate what the MBA is all about.
The London Business School website has a pretty good one-page summary of who the MBA is targeted at. Different schools vary on the exact demographics mix both pre- and post-MBA, but I think it’s helpful to point out the vertical move and career switch aspects (I personally feel that intentional, dramatic career switch is the most common reason). I am less in agreement on how helpful business school training is for entrepreneurial start-up situations (having participated in this type of environment), but the experience also varies by school.
Business Week and some of the other magazines used to run pre-MBA salary versus post-MBA salary numbers. Sometime you can also get this information from the schools. Some of the schools also go one step further to show the payback, ROI, etc. analyses.
List of MBA bloggers is also here (mostly current MBA students as opposed to alums). May be useful for people to tap into that source of info.
Update (3/19/05): 2004 survey info from Graduate Management Admission Council (GMAC®) which provides additional information supporting my comments on career switching (switching industries or job functions).