What do brokers do with their deposits?

When you deposit money into your forex account, what does your broker do with it? Sounds like the forex market is similar to the commodities market in that margin and deposits aren’t actually used towards your purchase. They are just a good-faith deposit. So what does the broker do with their customers’ money? Do they invest it?

[video=youtube_share;gBLeVcP_JQg]http://youtu.be/gBLeVcP_JQg[/video]

When you don’t trade they keep the money in segregated accounts (at least honest brokers do), when you trade, they use it as collateral for your trades towards their liquidity providers.

I think the broker keeps the money and give you access to trade forex and to buy and sell. I am sure they won’t invest the money because they know that a trader can request for withdrawal at any time. I have about $1000 in my Profiforex account. I am not scared about it because I have made withdrawals several times. So if they invest my money in something else, I don’t really care, as long as I get my money when I needed.