[ QUOTE ]
Or, you could design a trojan that after infecting a user's computer is designed to notify you when that player is playing online poker at a specific site, say, by sending you information via an IRC channel.

[/ QUOTE ]
You would still have to identify the recipient as a player, and get it to the computer. Blunt force (trying to send it to everyone who opens an e-mail or a web page) would certainly get noticed fast. I could see someone's "friend" doing this, but that's about it.

The "trojan" in the other thread has been questioned by posters with a background in security. (And others with a background in poker.)