What I would be interested in - is the daily funds movement details for PayPal. A couple of weeks' worth would be enough.
Consider the value of funds that pass through their hands - and the time it "takes". You come up with a number that is impressive - and it's like a dam. Water flows in and water flows out, but there is still that huge body of water that sits there. Yes, it is completely replaced every few days (on paper, anyway) but that volume of water still sits there behind the dam wall.
So, what do you do with all that water ... just look at it? Maybe - but if it's money, you'd be mad to do that.
Take the fourth quarter of 2016. PayPal handled $99 billion in total payment volume. Let's call it $1 billion a day. Assuming all those funds are drawn in from other financial institutions, "processed" and then 5 days later are deposited in other financial institutions, then PayPal will have a $5 billion "float". If you were to take into account the funds that account holders keep in their "PayPal Balance", this number goes up.
So what would you do with a $5 billion float? If it were me, I'd be looking at the short term money market for starters.
The thing about this arrangement is that it is soooooo easy to cover bad investments or - which is a real operating risk - getting caught out by wild exchange rate fluctuations ... just slow up the passage of funds. Make it take 10 days instead of 5 and you have an extra $5bn to play with. (Does anyone remember any such "coincidental" events like this? I do.)
Now, I don't pretend that these figures are completely accurate for the purpose of calculating share dividends - but they are an indication of the order of magnitude of what is in play.
In a nutshell - PayPal isn't going to be worried too much by fraud at this scale.
IMHO