thanks for sharing, it was an interesting video.
But if it's a hot topics then
many different forums will have it. Why not discuss unique topics that arn't as easy for other forums to get, and original?
If you do that, will the members be there because they legitly like your forum, or because they'll get something from it? It's like with your friends; do you want a friend who talks to you and is your friend because you give them things or because they really like you?
Do you mean via Email? If you're constantly sending out reminders to people who really don't want it, you'll just be irritating people (which, in my experience isn't a good way to get members).
Just getting this out there, that when you just post "Welcome." or "Welcome to __" you're not really welcoming the member. You're upping your post count and that's it. Why do I say that? Because just saying 'welcome' doesn't make the member feel welcome. I've found that posting a few words about yourself, directing the new member to a helpful or topic that you think may be of interest to them (by their avatar, username, or introduction), or asking them a question or two can get them into the community more.