This relates to Cleanfeed which BT and a number of other ISPs use (VM not being one of them).
The Internet Watch Foundation supplies lists of dubious URLs to ISPs which run the Cleanfeed service. Rapidshare no doubt has its' share of kiddie porn. When a site is added to the list the IP address of the server it is hosted on is routed through a Cleanfeed proxy, so you get the usual proxy effect from Rapidshare.
The issue is that Rapidshare don't use the X-Forwarded-For header that proxies give to websites, if they did they would see the IP addresses of the clients, as it is they only see the Cleanfeed proxy.
Either Rapidshare can start trying to sort it so that people don't use their service to hold kiddie porn, or they can start reading the X-Forwarded-For header.
I consider Cleanfeed to be a perfectly acceptable and well implemented solution, sadly if Rapidshare aren't interested in reading a simple header there's not much that can be done. Cleanfeed helps reduce child abuse on the Internet and functions in a standards compliant way. Rapidshare are being lazy, and have been for years.
Conspiracy theories over I hope, it's what I mentioned above, that's all, nothing to do with blocks to lower bandwidth bills, BT intentionally blocking people or whatever else