This argument is such an annoying fallacy. People who use Google's services are Google's "customers" in the same way people who watch television are the network's "customers". You may not be the direct source of income, but if they lose all the "non-customers" that are using their services, they're going to lose all of their advertisers, which is their direct source of income. The audience is a crucial component in a business model that depends on advertisement.
Even if it wasn't, Google opens itself to criticism and review whether their service is free or not. We definitely shouldn't temper our ideas or give Google a pass because "it's free"; that might excuse some advanced features, but it definitely doesn't extend into basics like contact exporting. That's a fundamental, and something that many have blasted Facebook, also ostensibly a "free" service, for not supporting well.
Google is making money off of Gmail. If they weren't making money off of Gmail, they would have discontinued the service a long time ago. Even if the nominal costs exceed the direct profits gained from Google Apps licenses and the display of AdWords, etc., which I tend to doubt, the indirect benefits are obviously valuable.
Should we all feel a great gratitude to the for-profit corporation Google for pursuing their best interest? Certainly we all appreciate the free services, but Google is no charity and expecting an altruistic, anything-goes attitude to their products is silly. They are a serious company making serious money and competing in a serious space, there's no need to make up excuses for them, especially naive ones like, "Well it's free anyway so you shouldn't expect anything out of it".