UserX has been awarded the 'Someone Likes You' trophy on websiteexample
Click here to view all of their trophies!
Now this wouldn't be a notification every single day, unless you have a very active member. It would not be spam.
There are cons and benefits to this feature.
I'm not commissioning anyone to do this, but I'd gladly pay a few bucks for this add-on if someone develops and releases it.
This also doesn't have to be just Facebook (I don't really exactly like them, but my users do). Myspace, Twitter, Google+, or any other popular social networks.