For in-game currencies so far, the centralization has meant two strikes: one, fear of the proprietor's control; two, the risk other entities (governments) could exert control via pressure on the proprietor.

Emergent decentralized currencies address both – and might also improve centralized-proprietor currencies by competition and precedent. (Proprietors will accept more community input, and win greater tolerance from governments, because of pressure from alternatives.)

Exactly. In-game currencies showed the potential since they broke out to have value in the real world, but could never really catch on beyond those gaming subcultures due to the friction involved. Dogecoin's light attitude is a great marketing tool and will help further reduce the friction involved in using it.

The thing to watch for: when another online community embraces the dogecoin tipbot culture. That would be a strong indicator of long-term stickiness. The OP joked about having no /u/dogetipbot on HackerNews, but that's exactly the kind of feature that I suspect will start turning up in a number of communities.

With regard to games, Valve hired an economist some time ago. I'd love to see if they have anything planned with regard to innovating in this space. Could you have an in-game currency backed by a cryptocurrency?