Didn't see any mention on their site, but do they allow any hardware mods? As long as it remains close to stock size and mods are durable to be handled in normal way shouldn't be a problem?
what's the reason to use a Pi as a server? it's a fairly slow board and can't compete with real dedicated servers? I think it makes much more sense just to use it on your own Internet connection for a small hobby project, etc rather than sending it to a datacenter.
You have unlimited fast bandwidth with that service? People in the world are still limited by ADSL/2/+ uploads. Most severe limitation would be the raspberry pi speed itself. Shared usb storage - ethernet bandwidth is not desirable for server applications. Run something like a dedicated low power 24/7 mumble (open source team speak) server. It's easy to setup a server and run it for 5 minutes, but try running it on a home connection for 5 months or 5 years. Also if you are worried your isp is monitoring/shaping your internet usage, make it your own VPN and your ISP or anyone listening won't have any idea about anything. Fast reliable internet enables all kinds of uses.
This is not a good offer if one sends away their only raspberry pi they could barely afford.