Hi Oli,
Thanks for bringing this up. I too am frustrated that we've only got ~1700 users. I can tell you what I've been doing to get this off the ground. (I am a Canonical employee but doing this because I think it's a great idea, it's not assigned to me or anything like that).
- Blogged on planet ubuntu. Tweeted a ton of times.
- Mailed the reddit/r/ubuntu guys to add a link (they have like 8000 people over there!) (No response yet)
- Asked teams within Canonical and Ubuntu to use and support the site.
- Asked Jono to post a link in the Ubuntu Facebook group, which he did twice.
- Asked it to be put in the /topic of #ubuntu to make that channel actually useful. (Got declined on this one.)
- Asked for it to be included in Ubuntu Weekly News. (Done)
- Sent in a voicemail announcement to the Ubuntu UK podcast. (Pending)
- Asked 2 LinuxJournal authors to tweet it. (One of them did)
- Started a conversation with the Launchpad developers about the future of Launchpad answers.
- Talked to the Canonical design team on help with the design and logos.
Unfortunately we still have a chicken and egg problem.
- Many people still "don't get" the SE experience, so we need help trying to explain it. For example see morberley's answer to this question, we're going to need this exact kind of help to make it work.
- Many people want to support whatever the "official" thing is. We can't become "official" until people use it and there's quality content out there.
I am open to any ideas, but please hang in there!