Yahoo bought the company near the peak of the dotcom bubble for more than $3 billion, which, along with the rise of alternative services, quickly spelled the end of GeoCities' prominence. Today, it appears that the end of GeoCities is being made official, as Yahoo has closed the service to new accounts and posted an FAQ with some details as to how the shutdown will go.
It's certainly not surprising that GeoCities is shutting down, as Yahoo has been in cost-cutting mode for months and the service would seem to have little fit in its current business. The company offers a fairly generic explanation of the move: "We have decided to discontinue the process of allowing new customers to sign up for GeoCities accounts as we focus on helping our customers explore and build new relationships online in other ways. We will be closing GeoCities later this year."