There is this common saying - never ever trust the internet. Facebook is not an exemption.
Facebook might have been built using the latest and top notch security softwares but there is also the presence of hackers who are tuned towards passing through security undetected and personal information can be compromised.
Earlier this year we heard of the news that facebook security was compromised and there was data leak inclusive of individuals personal information.
So if you ask me if we are to trust facebook with our personal information I'd say yes and no.. This is because facebook itself would never use our personal information without our permission and no because facebook just like every website on the internet is susceptible to hacks and information leaks.