Interesting idea. Two companies circling themselves in a death spiral from the heights of popularity may be able to grab hold of each other and keep from crashing to the ground. Stranger things have happened.
If they are smart they will rather focus on E-Commerce. That would be the best way to monetize their business as the biggest social network in the world having close to a billion viewers Young people love to shop. Therefore a acquisition such as TheFancy.com would be the best match for FB to make money in stead of getting in phone business