"It’s easy to forget just how exciting and revolutionary ICQ was. Almost overnight it took two of the most powerful features of the walled-garden online services—being able to see when your friends were online and message them in real time—and brought them to the Internet. People signed up in their millions, and for good reason.
Unfortunately, while everyone loved the service, it only took a couple of upgrades before the client software was universally loathed.
The problem was there was only one company making ICQ clients. Thus there was no competitive pressure to improve the core experience of sending and receiving messages from your friends, but boy was there pressure to add just one more advertisement panel, or yet another button to pump sponsored newsfeeds and stock quotes to millions of entirely uninterested college students."