You can get country targeted ones, which if done correct, you may end up with 1% who actually show an interest in what your tweeting / posting on Facebook.
They are great for the initial interest if you need more FB likes to get the unique URL.
Depending on where you get them from, depends on how long they will last. Fiverr is pretty much a waste of time for this. I know of 1 good seller of them on there. There is a system I use, and I lose about 2% in the first week, mainly as the majority of likers are real accounts, and not just spam accounts.