I searched to be sure I'm not posting something already known, but it appears this is different from other social networking offers related to Hilton posted recently. I received an emailed offer this morning to link my Facebook and Hilton accounts today to earn an easy 500 Hilton HHonors Points. Though I'm a TopGuest member and it is hosted on TopGuest's site, the terms don't seem to state that being a member of TopGuest is required:
http://doubletree.topguest.com/
Just enter your account, submit, and when it asks for permission regarding who can see the posts, select "Only Me" so no one is bothered. Once the points post, if you're really concerned, you could disable to app completely with no consequence. Enjoy!