I agree with Nark too.
In answer to the question, I think it's for some Christians, those who've been given that gift.
I belive that it is primarily a personal gift. I don't believe that a Christian who hasn't been given this gift should feel lacking or inferior.
I do believe that it is both mis-used and abused by some, and faked by others.
I wouldn't take the use of tongues by someone as any proof of faith, validity of belief or reason to follow and would be very cautious about anyone who attempted to use the gift in that way.
However I wouldn't reject anyone or their beliefs/suggestions simply because they claimed to have the gift of tongues either.
I personally don't have the gift. I know many people who do and my relationship with them is such that I trust them. I also know people who I doubt a bit (but that may be precisely because I don't know them very well) and I've seen those on TV (like the guy someone posted a picture of) who I'm sure is faking it (but hey I don't know him either!)
My research led me to exactly the same conclusions biblically as Nark, including the difference between tongues in Acts and tongues in Corinthians.