i think in the grand scheme of things, a seizure like silkroad isn't really going to do much anymore... except maybe publicize btc's even more. even if they shut down v2.0, it'll just leave a void for another group to fill.
yeah, if anything, i think the feds holding all those bitcoins is increasing the demand making prices higher than they normally would be right now.
And now that China has dumped so much money into it, I believe we won't really see a huge crash if we ever do see one. Exceptions would include some serious exploit that basically breaks the whole system, but lets pray something like that never comes about.