eBay responds with its own payment service , Billpoint .
PayPal adopts eBay as a key platform to grow its userbase , because of the need for an online payment system on eBay .
eBay responds with eBay 's own payment service , Billpoint .
PayPal adopts eBay as a key platform to grow its userbase , because of the need for an online payment system on eBay .