I logged into fb, sent to 3 friends, and only one got a link to get gc. By the others it just posted on their wall that I won. Anyone else having a problem claiming the gc's? And the one that got the link, got a message saying something to the fact, that the gift wasn't meant for them.
I just shared about 30 gifts amongst four FB accounts (2 on a desktop, 2 on a laptop- each one FF and Chrome Incognito), and did not have a single problem like that bH.
I would therefore assume that you are doing something wrong. Especially being that the only people I have heard of getting the "This gift is not for you" error is when they sent a gift to another FB account and claimed it on the same PC, without clearing cookies/cache.
Are your "friends" actually other people, or at least other PCs (or at least fresh cookies)?