Perhaps a tad sensational but this article suggest that IRC won't survive DOS attacks...

Could Attack on DALnet Spell End for IRC?
By Thor Olavsrud
For at least a month, distributed denial of service (define), or DDOS, attacks have been crippling DALnet, one of the world's largest Internet Relay Chat (define) networks, bringing it to its knees and raising the possibility that many hosting providers may refuse to host IRC servers at all.

"DALnet is presently suffering extensive and prolonged Distributed Denial of Service attacks against our IRC servers, Web server, mail servers and DNS systems," DALnet said on its Web site. "These attacks are causing great inconvenience and financial loss to many of the organizations that host our services, as such some of them have suspended or discontinued their support of DALnet."