Yea, the government might be able to trace who owns what coins... but how can we... how can we as regular people avoid buying some centralized piece of crap coin, with absolute certainty.
You can never do so with absolute certainty. You can filter out the obvious scams, though.
If something that is:
a) Promising high returns off your investment for doing nothing
b) Promising new tech vaporware that is probably too good to be true
c) or trying to get you to invest amounts that are larger than actually needed
It's probably a bad coin to invest in, and at best case scenario, a centralized shitcoin. Btcney has mentioned bit connect and i think that's the best example at the moment, massive ponzi that is about to blow up soon.