Newbie with 1 merit worth of $10, and jr.member worth of $30? That was insane holy crap!
It's more or less what theymos predicted:
Merit sales, transfers to aliases, back-and-forth trading, etc. are not much of an issue. All illegitimate merit will decay, and will account for a tiny and very expensive fraction of the total merit economy. It's basically a rounding error; fight it where convenient, but waste no sleep over it.
Add the fact that it's very likely the accounts don't even exist after "buying" them, and I don't expect account sales to cause that much spam anymore.