What are AB, A-B-C trades exactly?

[Useless]

Cool. I was hoping there wasn't something I was missing (and there often is). I love tagging. I use UTW on my top secret blog - on all 3 posts. But technorati and delicious tags seem like a nice way to drive traffic to their ads, and no real gain for the site using them. I think of tagging as a means of dynamically creating unlimited categories or classifications. Who ever invented tagging definately deserves a cookie.