Is exchanging of merits between alternative accounts a problem? What can happen with less than 50 merits?
Do you think this is not a problem?
I'm with theymos on this one:
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.