Go to Shopping cart with an item in it...
Try to update the cart... no matter what payment you have selected. If you click "update" the Paypal express checkout Icon/symbol will pop up underneath the regular checkout icon.
I've seen it on the demo site and my site... and I have tested with numerous payment methods selected and it doesn't see to matter which one is selected.
This is a major issue if you do not have paypal express.....users may want to use paypal.. but it's not set up.... they may give up on buying anything.