How do you even begin to make a return on this money? Put redirects in a frame and put an ad in? Charge for some sort of premium service and hope people don't go to one of many other url shortening services?
If AOL, Microsoft, etc wanted to set up a url shortener, it might be worth their while simply obtaining the technical infrastructure, domain knowledge of the staff, business deals and of course all the existing links + data then to just start their own from scratch.
(Mind you having taken $14m-$15m that does now make it an expensive aquisition. I'd have thought it a no brainer for the AOL/Microsoft/Yahoo's to pick up bit.ly for $20-$40m)
How realistic it is that that will be a home run for them, I'm not sure.
But at some level of complexity in functionality, reporting, etc it'd have to be attractive to people to just make use of another service. e.g., we can build a newsletter system that is OK, but the bang for buck that MailChimp provides is greater and so we often recommend that to clients.