I second that suggestion. It would make the extension that much more awesome to not have to block sites on each device. Might also help to lower the noise on Google's end, so they're not seeing multiple blocks on the same domain from the same users, though I'm sure they account for this already.
It's a bit difficult to implement sync of arbitrary data in a Chrome extension now. The extension developer has to setup their own storage and implement their own sync code. Either that, or some developers just store their data in the bookmark system, which has its own problems (please don't do this Matt!).
We (the extension posse) are working on making this really easy to do , but nothing exists yet.