Spam and Spim, modern-day gunslingers.
The Register has a nice backgrounder on the scourge of Instant Messaging, SPIM. It stands for spam-laden instant messages. Buddy lists can block them, but woe to those who don’t.

The fact is, spim is not entirely new and long-time IM providers like AOL have been fighting the problem since IM was first made available. But whereas early IM fraudsters often sought to steal AOL account details, today’s version is increasingly interested in selling goods and services, with some 70 per cent of spim messages pointing to pornographic websites. Around 12 per cent involve “get rich” schemes; product sales account for nine per cent; and loans or finance messages are at five per cent, according to (the) Radicati (Group).

Still, most analysts have admitted that the spim problem may never grow to be as big a problem as emailed spam. But the intrusiveness of spim - with messages popping up on screen - makes the format somehow more insidious.