Why was the Perl 6 Advent Calendar such a Success?

I think it's not too bold to call the Perl 6 Advent Calendar a full success: over 40k page views, more than 150 non-spam comments, and lots of new faces and nicknames in #perl6 - it's been a very pleasant surprise.

I asked myself why it became such a success, and came up with this list of things:

Limited in Scope

24 days are over rather quickly, so everyone who contributes knows when the deed is done

It appeals to very different contributors

Some people like the shiny new regex and grammar features, others are interested in the object model, operator overloading or complex numbers. Since we had no fixed topics, everybody could choose a topic that played to their strengths.

Each task is small and well limited

Writing a good post about a topic you know takes about half an hour up to an hour, maybe two if you need to do some research on the topic. Either way it's a relatively small task (compared to "write a regex engine" or "redesign the build system of $compiler" or so).

Schedule and polite nagging

We had a schedule for each day, and people could add their name to a free slot. When the day approached, the other authors started to ask politely how it was progressing, making sure people did not forget their posts. Also authors felt the subtle pressure to finish their posts on time.

Lots of positive feedback

We had lots of feedback, most of it quite positive: blog comments, visitors in our IRC channel, being featured on slashdot. That was very encouraging.

Also other authors would preview and proof-read the posts before they were published, pointing out falsities and gems.

We had a driving force

PerlJam and colomon took care. The decided to make the advent calendar happen, set up a blog, discussed things and so on - they made it happen.

All these factors encouraged contributions. I don't think all of them are necessary for a successful, lively projects, but they certainly help.

What other factors do you know that encourage contribution in open-source projects? What could we have done even better?