Faction bank?

What's the point of depositing funds into your faction bank? And can you take them out for yourself again?

Well, technically the faction "bank" is just the armory. Make sure you trust your leader / leadership to give you your money back if you deposit it. They are under no obligation to give you anything that you put in the armory, and could just take it all for themselves. 

I suggest you look into alternative methods of banking your money. 

There's a good section in the guide titled "Baldr's Basic Advice" that covers many of the ways:

https://www.torn.com/forums.php#/p=threads&f=61&t=16034448&b=0&a=0&to=18301183

I suggest reading the guide in it's entirety when you are done.

you cannot take them out yourself, someone with a banker role must take it out for you, as for whether it's worth it, depends on if you can trust your faction leadership. If you deem them trustworthy enough, it gets it out of your wallet and cannot be mugged. 

if you're worried about the trustworthiness/safety of your faction bankers/vault, you can always use stocks to self store money.

here's a lil guide:

Infinite Money Storage (No Vault/Faction Required)

Hello I am trustworthy. You can send your money to me