Almost any inbound link on Facebook should be of some help with the search engines. What should really help is the steady traffic from people clicking directly on the links.
You want as many incoming links to your site as you can get. That being said, they should be reputable sites and Facebook is certainly such a site. Google judges your website for search engine optimization purposes partly by how many links are incoming. Facebook can help a lot.
I read on another thread that Facebook links are what is known as no follow links. I'm not sure if that guarantees that they will not be followed, but I wouldn't count on Facebook for search engine optimization if this is correct.
- Does the product or service suit Facebook ? - e.g. fashion yes, insurance no.
- Is the site up to scratch ? - I would always prioritize this first rather than helping Facebook get even bigger
Facebook is suitable for any kind of product or service, however it is essential to develop a network there. Once you have established a network, promoting the products or services becomes easy and effective.
Links posted on the Facebook Wall or Fan pages are nofollow links so you shouldn't consider it to be a backlink but it will definitely give you a benefit when it comes to popularity.