Social news aggregator Reddit.com announced Monday that its chief executive and lead developer Christopher Slowe is leaving the company, even as the site experiences a year of unparalleled traffic success.

Slowe, who has been with Reddit longer than any other employee, is joining the airline flight search startup Hipmunk, home of Reddit cofounders Steve Huffman.

“It’s incredible to think that, back when I started working at Reddit five years ago, our monthly traffic totals were 38k uniques and 750k impressions (incredibly we now do more than that every hour),” Slowe said. “Though over the years we’ve had a fair share of bumps and outages, I daresay we are now thriving, and after a lot of thought I’ve decided to leave Reddit (the job part anyway) on a high note. This community has accomplished so much in the last few months (to say nothing of the previous years) that I can’t help to be humbled and proud to have been a part of it.”

Reddit’s community manager Erik Martin said the staff of six is sad, but that with the successful Jon Stewart/Stephen Colbert rallies on the Washington Mall this past weekend, it was the perfect time for Slowe to announce his departure. “(I am) ‪sad‬. Why are my eyes sweating??!” said Martin. “‪Chris saw us through some really difficult spots‬ and this weekend was so triumphant and awesome. We got to meet so much Reddit family. It’s the right moment for him to move on to the next challenge. So, it’s sad but feels right, and‪ I think five years at one company is equivalent to Dark Side of The Moon staying in the Billboard Top 200 in the internet world‬.”

San Francisco startup Hipmunk hopes to beat out other flight search services by letting user see several possible flights in a grid layout. It also, among other features, eliminates less desirable flights automatically. Martin says Reddit’s loss is Hipmunk’s gain. “Chris was our lead developer and had a PHD in astrophysics. It won’t be easy. Fortunately our community is filled with lots of sharp engineers and we’ve always hired from within the Reddit family so far.”

A good portion of Reddit’s 2010 success was built on a rival’s missteps. Digg.com attempted to change the look and navigation of its site at the same time in late August. That move resulted in glitches and errors, as well as user anger, that lead to the loss of much of the site’s traffic. Many of the old Digg users set up camp over at Reddit and have not looked back.

Slowe was quick to assert that his departure had nothing to do with long-rumored friction between the site and Conde Nast, owner of Reddit, as well as Wired.com, among others. “To kill any conspiracy theories in the cradle, my parting with Conde Nast has been nothing but amicable,” he said. “I have no doubt I’ll be partaking in an odd job now and again on the site.”

There has always been a bit of a conflict of interest however between the more profit-centered mission of Conde Naste and the more community-oriented mission of the site moderators themselves. “‪Of course‬ (the conflicting positions can be a source of frustration),” said Martin. ‪”To be fair they have left us alone‬. Sure they would like for Reddit to bring in more revenue but they have been pretty hands off all around. R‪eddit’s community is what sets it apart‬. (It) was so gloriously evident this weekend and we see ourselves as janitors or groundskeepers at an outstanding museum or amusement park. We’re just trying to keep everything working and running smoothly and occasionally introduce a new feature or two, trying to make enough money to do so, and do so in ways that improve the community’s experience.”

Along those lines, Reddit specializes in more integrated partnerships that allowed advertisers such as Microsoft to hold ongoing conversations with community members in certain “subreddits”, or specialized sections within the site. To continue the theme park analogy, Martin notes that some of the best rides are connected to a brand, such as the Batman ride at Six Flags for example. “Advertising is something that can improve user experience or make it suck and while there is a balance in generating enough revenue to keep the site up, we are always trying to find ways to incorporate brands that contribute to the user experience, or at least don’t make it suck…. As for Microsoft, t‪hey are advertising with us again for some other things‬ so i guess they were happy with the results,” Martin said.