Normally for a business, credit card companies 
take 3% on every transaction.  Through Paypal,
they may not charge them at the same rate.
Paypal actually doesn't make much money if it 
stays as a free service.  Like Yann said earlier, 
Paypal only make a small amount from the bank 
interest.  And when people use credit card to pay, 
the bank charges them too.  Paypal did it for free 
earlier just want to get many people sign up its 
website.  Now they got over 3 millions users, now 
it's time for them to roll the dice and make 
serious money.  Many Paypal users are pissed that
they started the fees, but since it's the most
popular payment method in EBay, you just have to
follow the wave and use it.