Kinless has a good post on Blizzard loves and/or hates Alts. « Kinless Chronicles. It does seem a little odd that with all the effort Blizzard has gone to to promote alts, they have refused thus far to provide any extra character slots.
I really enjoy playing my alts. So far I only have four 80s, with a smattering of 70s and a mage I’ve been running low level dungeons on as part of a group. I wouldn’t be surprised if I have seven or eight 80s by the time Cataclysm comes out. At this point, my extra character is an alliance toon I use for cross-faction shopping, but I would prefer not to delete him. One of these days I was also hoping to transfer and level my first character, a priest. I would really love to have at least one slot per class.