Facebook doesn't add backlinks for your website but can help build direct traffic which Google likes. If someone likes your Facebook page and you keep it updated regularly then they will remember your business. The only problem I have is that the websites I build don't really build an interest with the public as we usually sell to businesses. Therefore Facebook might not be the way forward for ourselves although we still have a fanpage just in case. So if you have something that might be of interest to a range of people that use Facebook then set up a page to keep your customers up to date
No. I like to think of it as more likes = more people like it = some of those people are bound to be webmasters = some of those webmasters might link to you.