Facebook can be good... BUT do not forget to MIX your traffic strategies. Personally I believe in 3 different marketing actions: 1) Actions for the present 2) Actions for medium time 3) Actions for long period For example, classified ads send nice traffic for present and link-building is very powerful in the long period. Financial investments use the same tactics to win the market.
You got to promote your product the right way to avail from this service!. Promoting a product through Facebook really works for most brands. It is working real nice with a couple of my friends.
some product succed with the help of facebook , while some dont , try out different niches and you can succeed i think.
Read this http://www.allfacebook.com/shocker-3-to-7-5-of-fans-see-your-pages-posts-2011-06 and this http://searchengineland.com/report-only-3-to-7-5-of-fans-view-posts-from-a-facebook-page-82732
You can check out these two facebook webinars Webinar 1 No Optin Needed Webinar 2 No Optin Needed hope that helps
I can say it is a success for me but at a far distance from Twitter. I managed to put a lot of content via api ( automated ) to twitter and the sales just busted!