Some offers only credit through Facebook - watching a video, clicking through to a Facebook page, etc., so you need a Facebook account in order to get credit for those offers. Just like some offers require you to give your address, or zip code only, or download a program - some are Facebook only. I think via.me is a way to connect with your friends via your smart phone, and they have a FB app.
If you don't want a personal facebook page, you can create one just for your online reward programs. That way you can get credit for FB-only offers without really having to maintain a FB page.
I won't download stuff to get credit for offers, so I skip them. I don't have an iPhone, so I can't do any offers that require me to download an app on my iPhone. Just the way it is.
Hope that helps!
