I have no idea if this is specific to our instillation or not, but I tried it on a couple of our sites with the same result (they all use the same hosting provider though).
Someone else would have to confirm it on theirs but:
Under "User Tools" if a user assigns a domain to their account, and uses uppercase letters DomainNameLikeThis.com they end up with a redirect loop when you try to visit the site. domainnamelikethis.com has no redirect loop.
Don't even ask me how long it took to troubleshoot the problem to figure out it was a CaSe IsSuE. haha.