Chess.com is running on the sheer will, dedication (and financial backing) of a very small group of people.
The site has experienced tremendous growth typical of the web 1.0 days. When this happens, server, bandwidth, and human resources are quickly stretched to the limit resulting in periodic performance problems.
As Erik had posted in the history of Chess.com, it's popularity has garnered some jealousy among its perceived rivals as well resulting in some malicious attacks.
A donation function is probably soon in the works and I strongly encourage anyone out there who enjoys the site to dig in and offer a sign of monetary thanks for the wonderful effort demonstrated by the dedicated team who have brought us this site.
I've had a couple of extended outages with the website. Is there something wrong with it?