Webcest is like the act of incest, but in cyberspace. This means you can't do it without your computer. The phenomena of webcest was first unvieled by Jeffery Rowland, an insane billionaire who chronicles his life on the inter nets. Rowland found out that Webcest is the number one crime committed in Mediocre Britain, where it is too expensive to date other people. Also, wireless hotspots abound in this small island-nation.
Webcest most frequently occurs when direct back-door ethernet connections are established with the Pentagon, and people's judgement get all screwy. Using leet hax, it can be assured that two-headed internet babies do not plague PC users, but otherwise webcest is very risky. Mac users do not have to worry about THI-Bees (slang for two-headed-internet babies used in chatrooms). Mac users also have the highest rates of webcest, because their laptops are awesome.
Also, Rebecca, let me know if you find my wallet on the overpass near your house. I think I lost it there.
Webcest is looking for porn on the internet, finding your sister, and masturbating anyway. Webcest is starting to cyber with someone, and then doing this: "I CUT OFF MY PENIS AND SHOVED IT IN YOUR THROAT." If the other person says to continue, that's webcest. Webcest is noticing the birthmark at the top left of the Goatse guy's asshole.