eBay (NASDAQ: EBAY) has agreed to purchase Braintree, a VC-backed payments company, for a reported $800 million. eBay will bolt the company onto its PayPal division to boost its position in the mobile payments market. Braintree helps online and mobile businesses accept credit card payments by providing a merchant account, payment gateway, recurring billing and credit card storage. Accel Partners, among others, is eyeing a big payday with the sale. Accel announced a $34 million Series A round for Braintree in 2011 that valued the company at about $83.7 million.