AIM is automatically installed on your PC if you are one of millions of AOL subscribers. And if that wasn't enough, they really started to dominate the market when they bought Netscape, and began including their software with Netscape Navigator. Navigator was at one time the most popular Internet application ever, and its brand name is still very recognized. Apple is rumored to have some sort of deal in the works as well. AOL also has the opportunity to make lots of money by displaying advertising banners in their software.
More people using their software means more advertising revenue.
It's clear that advertising to the 61 million registered AIM users and 80 million ICQ users is a big business opportunity. It's possible that AOL's Instant Messenger may have been installed on your PC without your knowledge. That's because Real Networks has a deal with AOL to automatically install AIM on your system whenever you install their popular RealPlayer software. AOL is also working with various hardware manufacturers to include access to AIM on all kinds of portable devices, from Nokia cell phones to Palm Pilots. You can bet that running AIM on these devices will be a top priority.