Unfortunately I think you're right about Facebook. If you're not on Facebook you're putting yourself at a significant disadvantage in terms of reaching a broad audience. If you're a small customer-facing (i.e. not B2B) business or grassroots organisation you need to be on Facebook.

But I just don't think the same thing is true of Xitter. And hasn't been since long before paedo guy bought it. Average people don't use Twitter and never have. It's used by a smaller group of journalists, techies, and the terminally online.