I'm not sure I understand, Isn't google now a direct competitor. They are now competing with you, recurly, autorize.net and every other billing company. Everyone will now use google checkout to pay monthly fees and their Gmail user name to sign into web apps?
1) A rising tide lifts all boats. I suspect this isn't a zero-sum game.
2) Chrome Web Store appears to be more geared towards desktop web apps. We're solely focused on mobile web apps. This is a key differentiator as the use case, experience, and expectations are all different. But Google pushing web apps as a legit form of apps will help us as we push mobile web apps as a legit form of mobile apps.
iTunes isn't the only music vendor.
They might be the biggest and most popular, but they aren't alone. =)