I loved learning about what the Incident is. Basically, a release of electromagnetic energy due to their drilling in that spot. Apparently it causes a catastrophe and similar to Chernobyl they have to cement it in and use a computer to release the energy so it doesn't build up.
This is the first confirmation, but it's been widely speculated that this was the case since "Live Together, Die Alone."
I love that. It is also my theory that The Incident might be the cause for why babies can't be born on the Island now.
Less obvious but totally plausible. If this is the case, I hope Juliet has some hand in making it happen. Talk about irony.