Glad to say I've successfully managed to register for the iTunes Match service even being out of the US (I'm in Singapore!) I can confirm that it asks for a US credit card but it will charge your account balance (as it did with mine) if you have sufficient to cover the costs of the service. I am neither a Mac or iOS developer and obtained the beta software through a alternative source. Also, it seems registration has been closed as I got the same message you did when I turned off and on the iTunes Match service (just exploring)
Can't say it's been very impressive though, it managed to 'match' a amazing *gasp* 280 songs out of 1188 songs from my VERY mainstream library. (Coldplay, Leona Lewis, U2, Lady Gaga etc.)
Attached is a screenshot
I do hope this is a 'beta' thing because the service needs alot of polishing before it can be released to the public.
damn yea thats what i'm getting. i guess they closed the loophole