socks or http proxies are dependant on the speed of the box they are on so one isnt faster than the other. You could band together with a few folks and get a server, even a cheap one then install a socks irewall and connect to that firewall, if it was a dedicated box with the socks firewall and thats all you wanted to run on it with a cheapo 100mbit server you could offer 120KB/s to about 100 people simultaneously, meanign it would cost each user $1 for the server cost (assuming the cheapo server is $100 a month).
That probably sounds good, BUT you need someone to front the cash and be able to still pay the bill if no one else pays (you know how people are sometimes), you ned people to split the cost with, you need a technical admin to run things (probably could get someone to offer thier services for free, just make sure they're not one of these idiots who thinks they can run a server because they have suse or mandrake at home) and lastly, and most importantly.... you need the socks firewall, which isn't open source so you're going to need to pay because as far as i know the now depreciated free version is nowhere to be found and thats not exactly something floating around the warez scene.
You can look into copycat proxies and free alternatives but more time will need to be spent with those, what I'm basically saying is it is totally feasable but its not a setup and run job, you'll have to at least be dedicated enough to run the server and keep track of who needs to pay and when. I say go for it. Oh and there are similar services out there already but you could tweak yours for iBurst users to make it more efficient. Of course peopel could always buy themselves VPN access for $10 a month with 10GB upload+download