Eating your own dog food doesn't work if you're a cow
AOL finally realized that corporate use of email is different than personal or small business use of email. All I can say is "Duh!" Here's what happens when you disregard your users' unique needs and go chasing after false cost savings:

Bad corporate mandates trap users in a bad situation:
Not all corporate mandates are bad. Homogenity and standards within a company can save money and create a healthy environment for good user support, reuse of code, and less training and re-training. BUT you have to pick the right product based on the business and user needs. AOL obviously didn't do that:

"management got months of complaints from both senior and junior executives in the divisions involved, who said the e-mail system, initially designed for consumers, wasn’t appropriate for business use. Among the problems cited: The e-mail software frequently crashed, staffers weren’t able to send messages with large attachments, they were often kicked offline without warning, and if they tried to send messages to large groups of users they were labeled as spammers and locked out of the system. Sometimes, e-mails were just plain lost in the AOL etherworld and never found. And if there was an out-of-office reply function, most people couldn’t find it."

AOL was clearly focused on cutting software licensing costs by using their own product. In doing so they also figured they'd quit helping out their competitors like Microsoft by not buying their software. While they were at it they should've just switched all their business users over to AOL dial-up accounts using a 56K modem. Of course, with no better, more usable option, AOL employees searched for ways around the horrible product that some myopic decision makers cursed them with:

"The e-mail problems have led many staffers to resume pre-Internet habits. Employees say they are faxing and using Federal Express more than before. They also are picking up the phone or wandering down the corridors in search of human contact. “If all goes well, we’ll never have to use e-mail and we’ll have to start talking to each other again,” says one magazine writer."

Businesses that allow decisions to be driven solely by false cost savings at the expense of business productivity and user needs will only drive costs up. One can only guess what this has cost AOL. Think about that in terms of real dollars, personal careers, inside political implications, employee turnover, and end user pain. Now instead of moving to one good unified solution, they'll have multiple products in use. One bad corporate mandate can spoil the appetite for any future mandates and the possibility of any corporate standard.

While it may be a good idea to eat your own dog food sometimes, you shouldn't make your business and thousands of employees suffer when your product won't work for them. If you represent a large herd of cows, making them eat your dog food is just plain stupid. If your product's target market is dogs, then just make it the best dog food you can. If AOL wanted to compete with Microsoft Outlook for the corporate email market, then they should have improved their product to compete in that space. Once they had a competitive product, then and only then should they have considered deploying it across their whole company.