That's very true, but digg never had the kind of stickyness that reddit had from early on. I think reddit has a stronger sense of community and I think that users may well be more attached to their communities than they are to their mods.
Until someone starts one … heck you are looking at one right now; specialised but it works in more or less the same way (with more restrictions on downvoting).
That's true, and puts reddit in an even more powerful position.
If those mods were anywhere near serious about this they should just roll their own reddit and attempt to migrate their communities. I'm pretty sure that would elicit an immediate response from reddit but that would be a much harder fire to put out than this one.
