Paypal verified user has many advantages over unverified user moreover they encourages members to become Verified to build trust in paypal community.
In unverified users once you have reached your sending limit, you must become Verified to continue sending money with their service.

* When you receive a payment: Log in to your account, go to the My Account tab, and click the History subtab. Find the payment in question and choose the status link (for example, "Pending") in the Status column. This will take you to a payment details page. Next to the sender's name, you will find that person’s Verification status (Verified, Unverified).

* When you send a payment: When you send a payment, a reputation link is provided where you may view the recipient's status (Verified, Unverified).

And most of all them ebay ask for the user to be a verified paypal account holder.(Correct me if I am wrong)