I guess that is a general problem with the whole 'freemium' approach. I use a number of such products and services which I greatly enjoy, but see no reason to pay for because their free offering is more than enough for my limited needs.

Had they said pay us a few bucks or go without then perhaps I'd pay, but when they say pay us a bunch for a service you don't need just so that the service you do need remains free for everyone, it becomes a lot harder to whip out that credit card.