I think it's worth pointing a few things out here.
1.) Remind me again what browser AOL uses? Oh yeah -- IE. Their contract with Microsoft ran out a few years ago, as I recall, after AOL had bought Netscape. What did they do? Switch to Netscape, their browser? Nope. They re-signed a contract with Microsoft to use IE. Imagine what would happen to IE's market share if all of AOL were to suddenly switch to Netscape. But no... AOL would rather try to get money from Microsoft because IE is dominant.
2.) Developing websites on Netscape is a nightmare. Period. To the point where I support Opera, IE, and Netscape 6. If you use Netscape 4, you're out of luck. It's support for CSS is awful, and I'm not even convinced that it knows how to render HTML correctly. Of course, when the majority of Netscape users use a browser that is 5 years old, your standards compliance gets a bit out of date too.
3.) Regarding Microsoft and competition (specifically, expensivelesbian's comment -- #3, I believe): Of course Microsoft hates competition. That's how competition works -- Company A wants to beat the tar out of Company B in the market. We have a word for companies that love their competition. That word is "bankrupt".