This is one of the more confusing abbreviations
that haunted me during my days dabbling in USENET
C&C means Coffee and Cats
OK, so imagine you're sitting at your keyboard , drinking a cup of strong black coffee, lots of sugar; on your lap is your white cat snowball.
You go to, say, net.admin.net-abuse.email, a newsgroup you occasionally read. You look at the various technical posts and whinges. Then you read something totally ridiculous -- say some spammer is threateneing to sue not just an individual for blackholing him, but their ISP, SPEWS, anyone who uses SPEWS as a blocklist, and USENET itself.*
That's it, too much. Someone is trying to sue a protocol, for fuck's sake. You snort in a mixture of amusement and disgust. But it's all gone terribly wrong. Your snort coincided with a sip of coffee, and now you've spat it all over your keyboard, ruining it. And your cat was so frightened by your reaction that it's jumped off your lap, scratching you on the way down, and is cowering in a corner.
This is why it's common courtesy in some online communities to mark some posts in the subject line C&C, meaning put down your coffee and clear away any pets.
Fine, in theory. Unfortunately, the really funny stuff is directly written by the kooks themselves, and they rarely think to inclde this useful warning.
* I've actually read a threat from someone to do this. He claimed to work in IT, too.