I get a lot of posts telling facebook will donate dollars if we share that post. But is it true? Will they really give? My experience is that if there is some contribution needed, they will declare it and even check with you if you would like to contribute as in the recent Nepal earthquake. 

I still don't know the answer for sure, so please comment if you know it for sure.

Facebook provide you option to get more likes by promoting the page and of course they will charge you for it. I do promotions and did recently too. And I was happy to see an increase of around 100 likes. To my surprise, after few days all these likes are gone. If I had done some like exchange or similar programs, it could have been due to invalid likes. But I had done the promotion through Facebook itself. This means either they are targeting wrongly or they are providing fake likes.