The general policy is to let nature take its course, and have topics 'sink or swim' depending on the frequency of posts added. Any subject not attracting replies would then, naturally, sink down (but would still be found by searching, of course...). Some topics, such as warnings about Paypal scams, are of permanent interest, and would normally not, in themselves, solicit replies; hence the pinning. It's also true that, when pinned, topics tend to become 'part of the furniture', and no longer receive any visits at all, because they're pinned..!
Having said all that, and recognising the quality and value of the OP, I'll pin this, as it's in the proper section for those interested. On my head be it, then; let the pinning commence..!