Most good Colo facilities offer "remote hands" services and will do whatever you need, often for a reasonable cost. Also, if you get your server(s) through someone like
www.ApaqDigital.com (etc), they have great warranties and great prices. I was concerned about all of this when I started looking but feel I have most of it covered now.
Just dumping your server in a colo without an research or options is at least as stupid as just leasing a dedicated server from someone without doing any research on the company at all...
I think I said this before but the colo I went with has not had a single outage that I have been able to determine in the 5-6 years they have been around. I even drove up there and met with them, talked service and ended up going with a sub company that has a lot of space with them who is giving me free hands on service if needed, remote reboot, plenty of room to expand and much more for the same price as the colo facility owner. Lot's of big guys in there as well and the DC's #2 upgrade (doubling floor space) will be online within the month, which speaks loudly to me about their growth.
Bottom line is research and planning pays off. I am very confident that the $500.00 + I will save each month will easily cover even the worst that may happen, and again, my server is rocking fast and built to my specifications.
If you are just getting into needing a leased dedicated server, I wouldn't look at colo. If you have leased dedicateds for a while and need to expand beyond one or two servers and have a revenue stream coming in from your forums (advertisers, ppc's, membership, etc), I would definitely look at colo options.
One more thing.. If you think the leased servers that hosts provide are high-end even if their numbers look that way, you have another thing coming. Most of them buy the servers you lease as cheap as possible, sometimes being refurbs, and with drives and other things that have been used for quite some time. They are rarely the top of the line server you would purchase if you were able to. If you don't believe me, just go visit some reseller data centers / cages and see what you see.
I'm not saying these servers are no good. I'm just saying that if you are serious about your community and it requires good equipment and uptime, wouldn't rather know the history of the equipment and that it is the best that it can be, rather than having a hodge-podge makeup of components, re-used drives (etc) you know nothing about?