if someone scams you over paypal
 

you open a dispute and if the seller does not respond is it guaranteed that you will receive a refund?

Yeah, as long as you escalate it to a dispute after you file with paypal.
Also they don't cover intangible items.

No, it will not.

They have to have money in the paypal for it to refund from.

And yeah they only cover "real" items. If you paid for design or something you are probably screwed.

My buddy had something filed against him for some LCDs he sent someone that took too long to arrive. PayPal decided against him, and they refunded the guys money despite my friend not having the money in his account. They then started phoning him saying he owes them money.

They may have changed their policy now to only refunding if the person has money in their account though, who knows.