Sounds kind of shysty to reneg on a deal like that. While there probably weren't many people who bought pre-paid cards, shutting it off and charging extra fees after they bought the card in the first place does not inspire confidence.
And what of this inactivity fee? Does it apply to people who have debit cards through google?
I ask because I work in Guatemala much of the year and obviously no one accepts the service here (or no one that I am aware of anyway). I would consider bothering with it, if it did not charge me and then I could use it when I'm back in the states, but if I were charged then I would just not have it on my phone.
I think the service needs some real work if they are approaching it like this. For example, I use PayPal infrequently 2-3 times a year, but I am never charged an inactivity fee. If I were I would never use PP again. But the company still manages to make money off of me with infrequent purchases. If Google is going to gouge me then I sure as hoot don't want to use their services.