If it weren't for my dynamic external IP address (which the ISP can't/won't make static) and not wanting to leave my noisy ass computer on all night (it's in my bedroom) I would definitely host a server. I have an old laptop that might be up to the task but I'm afraid it'll self-destruct and burn the house down someday.
I know of ways to get around the IP thing but it'll take some research. There's always third party hosting that's dedicated exclusively to Minecraft but it can be pricey.
Update: Unless we get another highly skilled benefactor with a spare LAMP box it looks like we'd need to get a Virtual Private Server going if you really, really wanted this to happen. Only catch is they don't come cheap. I guy from college swears by blacknight.com. They're an Irish hosting company and they're the most reasonable at €12.99/Month. If we got a few people to contribute it could be worth it but honestly I don't see enough people having an interest in this idea enough to cough up.