With the Open Source Database Conference over, I now have my doubts that this conference model is very viable. Here's the math: The PHP conference going on in parallel seems to have settled at around 350 attendees. The open source database market is, in my extremely rough estimation, about a quarter of the PHP market. (Almost every PHP site uses a database, but not all PHP developers are interested in open source databases.) Assuming again that PostgreSQL has about a third of the open source database market, that gives us a potential attendance of 30 people for a PostgreSQL track. The actual group of people following the virtual PostgreSQL track was about 20, but the growth potential does not seem too big.
Now what's the problem? Of course, the conference was advertized poorly and late. So perhaps improving that would give us the 50% growth predicted by my model.
The major fallacy, however, seems to be assuming that there is, indeed, an open source database community. There isn't. There is a PostgreSQL community, a MySQL community, etc. Throwing them all together is quite enjoyable for me as a developer, giving me the opportunity to meet the other groups, but for a regular conference attendee , it doesn't make too much sense. You see, there wasn't even a recognizable PostgreSQL track. You had to guess as to which talks related to which database system. A related problem is that there is not a lot of crossover between the PHP conference and the PostgreSQL track, something which is perhaps less of an issue for SQLite or MySQL.
But the biggest problem of it all is: It's just too expensive. The conference fee is about 800 euros; add to that the rather expensive hotel and travel, you're easily above 1000 euros for the two days. To see six talks about PostgreSQL (one of which you get to see for free again next week at LinuxWorld Expo Frankfurt). For that price, you can hire an expert on any database system to come to your site and train your staff for a full day or more. In fact, a three-day PostgreSQL training with room and board seems to go for 1368.80 euros.
That said, the technical education I received from this conference was excellent, including from the two PHP talks I saw. But perhaps it is indeed time to think about a PostgreSQL-only event with more affordable terms.