Also if they declare it publicly then those Merit sources inboxes will be filled up with PM asking for the merits. Theymos also told the exact.
It's fairly straightforward to work out who the merit sources are on this forum by looking at the merit received, and given. If someone was dedicated to pestering merit sources they would be able to figure it out. Although, I haven't had too many users message me to merit them. Only a few now, and again.