I've been highly active on this site since the very first days of the private beta, and been to the site every single day since then. (That's right,
313 days, 313 consecutive, since November 11, 2010 ;-) ). I don't always have time to do a lot of writing, but I check in at least once a day to try to catch any obviously bad or malicious posts, flags, and whatnot.
Within a few months I was appointed moderator pro tem, as one of the highest ranking users at the time (currently ranked at no.3). While I'm not on the site full-time, I do stop in at least daily, in case there is an urgent need of a moderator to clean something up. Even during pressured periods, such as project deadline, where I dont have as much time to read and write on the site, I make sure to check for flags, suggested edits, taggage, close votes, migrations, etc. Heck, I even logged on during my vacation on the beach... :$
In general, though, I believe the community should be mostly self-moderating - and the chief responsibility of the "diamond-mods" are to encourage and guide the rest of the community to do just that, with the occasional fine-grained mod-hammer if needed.
I think I've done a pretty good job with the encouraging - this can be seen in number of comments, more than twice as much as anybody else (well, most of them constructive :) ). As far as guidance goes - I believe in guiding by example, and well, I have edited and retagged more than 5 times more than anybody else.
As I said, I see my job as moderator (besides the occasional cleanup) as getting everybody else to do the right thing - though for the most part, most of the community pretty much does it anyway... And I like relying on my community peers to help with keeping the site in a good way.
As for the occasional cleanup - I'm in UTC+2 (and in the summer, +3), so I can usually pop onto the site earlier than most others. I don't hesitate to mod-hammer the obviously faulty ones (I'm the biggest closer), and try to get a consensus (or at least a second opinion) where it's a bit more ambiguous (or outside my level of understanding).
Btw, the above applies equally to Meta, the "town hall" of our community.
A bit about myself...
I have been active in the security field for just under a decade, focusing most often on the application security side of things (having been a programmer before, and now again). I like looking at how to make security efforts more efficient (but still effective), leading to things like secure coding, training, SDL, and high-level security engineering in general.
I enjoy publicising this site, and it complements my activities as a Board Member on the IL chapter of OWASP.... and, I recently talked StackExchange,Inc into sponsoring OWASP and becoming a member. In fact, at the recent OWASPIL conference, I was talking up the site a lot...!
One more thing...
A good moderator cannot help but make some mistakes, and as a great man once said:
"If you're not offending anybody, you're doing it wrong".
Of course we all try hard not to, but this still happens at times...
More importantly, in my opinion, is how one responds to disputes. I've been in my share of them (one might say I've used up my share of mistakes, so I'm safe from now on :D), but I've always diffused the, often tense, situation with respect and, if needed, firmness. As referrenced by one of the other nominees, I've helped turn one such dispute into one of the best contributors on this site.
I am proud of all I've done here, and by extension proud of the site and community as a whole.
This is what I want to continue doing.