Where is the link that you read this at? If you mean this http://promotions.newegg.com/PayPal/BTS09/P3_2/index.html?cm_mmc=EggXpert-_-na-_-na-_-na#terms I take it you did not read the terms and conditions.
Back To School Promotion Terms & Conditions
Receive $20 cash back on purchase of certain products (“Eligible Products”) totaling USD $200 or more (excluding tax, shipping and handling (“Offer”). Offer applies exclusively to purchases at www.newegg.com, using PayPal as a payment method. Offer begins at 6:00 am, Pacific Time, on August 18, 2009 and ends August 24, 2009, or until the Newegg website indicates that the Offer is no longer available. To receive cash back under this Offer you must: a) have a U.S. PayPal account in good standing, and b) complete a qualifying purchase of Eligible Products totaling USD $200.00 or more no later than August 24, 2009 at 11:59 pm Pacific Time. For purposes of this Offer a purchase is completed at the moment you finish the checkout process. The maximum amount of cash back per PayPal account is $20.00 USD. The cash back will be deposited into your PayPal account by September 25, 2009.
Excluded transactions from this Offer include, but are not limited to, the following: Pre/back-ordered merchandise and/or downloadable software, PayPal Pay Later transactions, PayPal Plug-In transactions (formerly named: Virtual Debit Card), gift certificate payments, gift card purchases, PayPal Debit Card payments, automatic and/or recurring payments that you have scheduled, and PayPal Plus Credit Card/ eBay MasterCard payments not made through your PayPal account. If the payment is refunded or cancelled at any time, you are not eligible for the Offer. If the payment is refunded after you receive the cash back, PayPal will deduct the cash back amount from your account.
PayPal and Newegg Inc. each reserve the right to cancel, suspend or modify part or this entire Offer at any time without notice, for any reason in its sole discretion. This Offer cannot be resold, transferred or combined with any other offer.