Right now, TRC has ground to a halt because it's difficulty was taken sky-high thanks to some ASICS that hopped on the network and then hopped off, leaving the difficulty incredibly high, and it taking everyone else forever to solve the block required to bring it down. It's brought the network to a standstill (although there is a fix being released for this).
Although of course TRC difficulties are incredibly low, so it makes this sort of attack easy to do- it does make one wonder how the bitcoin network would react. As we grow and grow, eventually we will get to a size large enough that we are threatening for various other interest groups (if we aren't already). Although ASICS have made it much more expensive to attack the network, they haven't yet become widespread enough to claim we are really 'safe'.
If a State actor (for example China) were to put some time and money into it, they as well could develop a line of ASICS (indeed the only functioning ASICS are out of china- the government need really only seize their already completed designs and pay the factory to seriously ramp up production). With a large ASIC farm one could take the Bitcoin difficulty so high that when they leave the network the remaining bitcoin miners are stuck for hours trying to solve one block. As TRC shows you need only to slow down block production by a couple hours to induce widescale panic.
Thoughts?