I just got a PayPal payment request from someone I do not know. A quick look shows that the payment link actulay goes to the PayPal site. So it is not the normal phising attempt.
On the details of the service listed it says "Post inclusion" and "Service".
So is someone just randomly sending out payment requests hoping that some people will actually pay it? Kind of like those domain inclusion postcards/letters where they they say in very small print that this is not a bill (yet).