I think it is unreasonable to check users previous posts for plagiarism before giving a merit. That would be a lot of work.
IMO, it's not unreasonable at all and I do this myself--especially if the post I'm about to give merit to was written by a low-ranked account. sMerits aren't exactly scarce, but I don't want to waste what I have on plagiarized posts. I've been saved from giving merits to plagiarists simply because I took about 30 seconds to google-check the post I was about to give a merit to--and that's happened not once, but several times.
I do not know how much Theymos will like, but I think we should remove Offtopic, Meta , Altcoin discussion board , Politics and society or any board not related to bitcoin stop giving any activity.
We might take a small fee while registering in this forum as newbie fee and those who still not able to pay that fees, might we create a guest board where they can still ask their questions.
I think those suggestions are a bit too extreme, and I highly doubt Theymos would go for them. The real solution should come in the form of rules laid out for bounty managers and those who participate in them. It's been discussed to death, but Theymos is slow with implementing forum changes and I think he wants to see how the merit system and the new changes he's made to it work before trying other things. That's just my guess, however.