Why is the SDMB membership declining, and what's the best way to add younger members?

Yes.

That board was moderated by snopes (David Mikkelson and most of that time Barbara) with assistance from others, and worked IMO pretty well until he apparently lost interest in it. There was then a considerable stretch of time during which there was effectively no moderation, and requests for anything requiring a mod or admin – including allowing new members to join, resetting lost passwords, and at least one case of a badly needed name change – went unanswered. During this time, not surprisingly, active posting fell off drastically; though the board had remarkably little trouble due to rules not being enforced, possibly in part because new trolls couldn’t join either.

Then we were told that the boards would close briefly while they were migrated to Discourse; and asked for updated contact info so we could be notified of the new location once it was up. And the boards closed down — and never reopened, on Discourse or anywhere else. The archives not only disappeared, they were banned from the Wayback Machine.

There are a number of others here who came over from the snopes boards. There are some references to the whole thing in this thread: Others here from snopes messageboard?

There is I believe a Facebook page. But that’s not remotely the same thing. Some of us tried to get a reddit going; but that format didn’t work for the purpose, and while that still exists last time I looked it hadn’t had any posts for months.