Hey Death,
As Per Wikipedia - A web crawler (also known as a web spider, web robot, or—especially in the FOAF community—web scutter) is a program or automated script which browses the World Wide Web in a methodical, automated manner. Other less frequently used names for web crawlers are ants, automatic indexers, bots, and worms.
Some web sites (Google, Yahoo, & MSN) do this all the time on forums to keep updated because of the type of traffic they have. If your on a lot of popular forums with the same screen name, you can google your screen name and see the spiders at work.
