Thanks. I understand the concern but think it will fade. When we have apps, I don't think people will be thinking about the domain when they get their app from the appstore. Also, some popular startups have been using it with success like Vine, Meerkat, VSCO, and Hinge. Twitter and Amazon use it for their share links.
I figured that if we get really successful, we could buy the cake.com domain if it still matters since it isn't being used. If I were the owners, I would sell it before we prove you can succeed with .co and the value drops.
You can see the downward trend of startups using .com domains at Y Combinator, the most prestigious incubator of startups: