Thanks for tagging me in @hawk!
We did do a lurkers week last year with posetive results (case study is here). Basically I tried to figure out some broad reasons a subset of our lurkers weren't participating and created content to address those obstacles. Do to limitations in measurement, it's difficult to report with confidence any substantiale long-term effect that links directly to that initiative.
That being said, I took what I learned from that theme week and applied it to a daily community content calendar - that means routinely posting successful content that was tested during Lurkers Week. We've found that using branded images and gifs with Lurker's Week-esque content has had a measurable effect on our participation levels (but that result is probably specific to the Facebook platform).
@richard_millington posted a great article on watching for spikes in activity - it feels great, but it's important to recognize that it's a short term solution. Community strategy should focus more on long-term results.
I've tried other theme weeks in the group that center around what our community likes to talk about - specifically, marketing strategies. I've found it's incredibly difficult to get these super dialed in. I think it's because our community comes from so many different areas of expertise and our members are in a varying degrees of business success. The subset that would participate in theme weeks is tiny.
For example, I tried to host an "Email Marketing Week" that failed pretty miserably.
However, "Traffic Week" got much more activity. That's because learning how to get paid traffic is a SUPER sexy topic for our members - it's one of the huge ways they make money as a business.
So I guess the moral of the story is, you have to keep your community's priorities and movitations tippy-top of mind when working on discussion themes (and community content in general). Work hard to diagnose the "why" when people participate or they don't.
Then, adjust and try again Don't get discouraged! Keep on testing, and use the info you get during short-term tactics to inform your communtiy strategy as a whole.