Apparently this was far from the first notification sent by disgruntled copyright-holders. Regardless, lulz.net's administrator appears confident of resuming service soon.
Update (11 March): The board is back up, apparently at Tocici.
The domain fchan.us appears to be in "serverHold" status, suggesting a removal due to financial, legal, or operational reasons. It does not appear to have expired.
According to Sein, the site has accrued nearly 75,000 files from 8,000 users since June 2008.
Update: As of 26 November, the site is back online.
Thanks to numerous threats to our host, false claims of illegal content, harassment and a few things that are much worse, e621 is being closed down permanently. It's been fun running it.
The closure is likely the result of allegations made earlier today that e621 hosted cartoon child pornography.
Yiffy.tk, one of the furry fandom's largest web portals and databases, has launched a new furry-orientated image board. Named Ychan, this mature-art only image board attempts to take on the giant that is fchan - either that or it hopes to replace the Yiff Image Board, which closed in February 2007.
Furry art communities Fur Affinity, fchan and E621 all went offline just prior to Christmas following an early morning distributed denial of service attack (commonly called a DDoS) against the three websites. Fur Affinity was back online by the evening of the same day, fchan was running with degraded functionality for roughly 24 hours and E621 was back online a few days later. The source of the attacks remains unknown.
A distributed denial of service attack struck furry art archive Fur Affinity and image boards E621 and Fchan on Sunday, lasting for several days. Fchan suffered from degraded functionality until early Monday morning, while Fur Affinity's main site was mostly unusable until the evening of the same day. E621 had returned by the middle of the week.
The initial burst of traffic was via UDP, a protocol not typically used by web servers, but blocking such traffic only worked for a short time. During the downtime, Fur Affinity popped up sporadically, with users reporting abnormalities such as getting logged in under other user's accounts.