One DM we had was a rules lawyer, another would just roll sometimes and weave great stories. It's been around fifteen years since I was in a group but I actually bought the latest players handbook a Little while ago, just to read. Lots of changes since ADnD 2nd edition. The first one I had came in a box :/
heheh, everyone knew the game mechanics well enough to rules-lawyer at the drop of a die. Sometimes the arguments would go on so long that the sun'd come up while we were still in the Button Room deciding one player's fate after the player having pushed five buttons.
(Stone room, 100 little stone knobs everywhere on the walls and ceiling, 100 different things happened if you pushed buttons, varying from awesome rewards to being transported alone to the bottommost level, to making an immediate saving throw against something probably mortal...)
The fourth Ed of D&D doesn't use THAC0 anymore. Which was a pretty silly setup to begin with, if you think about it. They designed the AC rules such that -10 was the best AC?!?! DERP!
I actually played in a group a year or two back with people I never actually saw in person. We played over Outlook messenger and XBL voice chat. The DM handled all the dice rolls. It worked quite well.