Yahoo! Search Marketing now offers PayPal payment option to advertisers. The tie-up announced yesterday will allow advertisers using PayPal to include a shopping cart icon next to their sponsored search listings, to signify that they accept payment via PayPal Express Checkout instead of (or in addition to) credit cards.
Google Checkout was in direct competition with eBay for online payment. They have combatted this threat by joining forces with Yahoo! in a move that will benefit both Yahoo! and PayPal to some extent.