If Facebook uses anonymous browsing data regardless of whether or not I am a user, that is not personally identifying and therefore harmless. If they want to go through the trouble of tracking my tendencies online, then that's okay as long as they're following the laws by not collecting personally identifying information without my permission.
If you have information on the internet anywhere it's possible for it to be breached by anyone. People need to understand that and unfortunately a lot of older folks don't understand the dangers that the internet can present. It should be printed on the website, user beware information could be breached by online hackers.
No. Facebook is no more capable of keeping your data safe from hackers than Yahoo or any other general platform on the Internet used for socialization and massive transfers of information. Whenever new technology is developed to safe guard information, there are always hackers jumping on the chance to figure out a way to dismantle it.
It is important to remember when considering safety is that your data is always being stored on a server somewhere in the world. These servers are always available to hackers, and should they try hard enough they can obtain this data. No security suite in the world can stop all hackers.