Go through your network. Do you know anyone that works at FB and LI? Do your connections know people that work at FB and LI (second-degree connections)? Chances are, you have a lot more connections at FB and LI than you might think. Ask your connections to introduce you to the folks they know that work at FB and LI and then schedule 30-min informational interviews with these folks. You now have a connection at FB/LI and can ask them what it's like to work there.