Your community is a brand. And it’s a brand worth protecting on third party communities and social platforms, especially the ones that you may one day engage in.
In other words, secure your username. I run KarateForums.com. What is the ideal username, on a platform I don’t control, for KarateForums.com? karateforums. If that isn’t available, then I have to settle for a much, much weaker second one. Try to be consistent on your fallback username.
No matter how great your fall back, people will always first guess that the ideal one is what you have. This impacts you when you go out to build outposts and community outside of your site. On Twitter, for example, they might guess that you are @karateforums, for example. It creates more work (and more missed opportunities) for you if you don’t have it.
But, having one is better than having nothing. I would generally recommend that you secure your username on Facebook, Twitter and YouTube, at the very least. This will give you facebook.com/yourname, twitter.com/yourname and youtube.com/yourname. On Facebook, you’ll need start a fan page and go to facebook.com/username. You may also need to have a minimum number of fans (previously, this was 25).
From there, I’ll let you decide what other platforms might be worth joining, in order to make sure that you have your username. You can use a service like KnowEm to register your username in many places at one time. But, for most, it will be preferable to secure it in places where you believe you may engage.
It is a good idea to be aware of any inactivity guidelines that the platforms have, as well. Twitter encourages you to login once every 6 months and post a status update, at the very least, to demonstrate that your account is not inactive. You should make sure that you do that.
Bottom line, take this as a reminder to put 15 minutes aside and secure your community’s brand on the platforms that are important to you.