Without getting into bloat issues of Monero, or Darkcoin instamine, a PoW coin, if actually able to achieve anonymous transactions, is in a difficult position. Governments would regulate against it, and PoW mining data centers are large attack vectors to be legislated against or just taken over. Yea, they would be located in many countries, but governments seem to cooperate a lot on things like drugs, so they might cooperate on issues like this too. I guess you could say Bitcoin sort of faces this issue as well, but they haven't made any big moves against it yet.
I would say that Bitcoin is even more at risk due to the ongoing centralisation of mining.
Where Monero is in direct contrast is that the PoW algorithm closes the performance gap between CPU, GPU, and ASIC mining, so even if ASIC miners are eventually created they will not be so significantly more efficient than CPU mining so as to make CPU mining pointless. Thus, in practicality, Monero could operate completely and entirely on solo miners with no pools operating.