Google forcing App Engine developers to use Checkout?

Developers who jumped on the Google App Engine bandwagon have gotten an unpleasant surprise. Those who create Web applications using Google's computing infrastructure have found that the Mountain View advertising broker is not-so-subtly asking them to use Google Checkout to accept payments and not rival online transaction processing PayPal, an eBay subsidiary. Valid PayPal domains "accidentally" got caught up in Google's anti-phishing efforts, according to Googler Marzia Niccolai.

Kind of like that anonymous complaint about eBay's anticompetitive practices in Australia "accidentally" displaying data which identified Google as the author. If the conspiracy theorists are right about Google blocking access to PayPal through App Engine intentionally, then why not just say that turnabout is fair play after eBay pulled similar stunts to keep Google Checkout off the auction site? That seems easier.