There are also those who do not give merits for even well written and highly constructive posts, they just keep s-merits for themselves to be given to their friends or prefered people later. Here in this thread I see a high rank member just posting a nonsense and already got 1 merit for that 
It is not totally fair, someone tried to abuse merit system, trading merits, exchanging merits, etc. But in general, merit system is good for the forum and its users. The forum has changed considerably after the launch of merit system some weeks ago.