Loz
Mongoose
I had a friend who used to work for a large gaming company (I won't say which one) and he had said that the reason many companies had scaled back on adventures, especially the smaller scale one-shot module type adventures, is that they just don't make money.
I think this is true to a large degree. If you have a regular group then once you've run an adventure that's it; you won't need to return to it unless your group completely changes. Also, only the GM needs to buy the adventure, which instantly reduces the size of the market.
There's more value in books that combine adventures with a setting, or settings that have lots of scenario hooks, and this is what we've tried to do with Dara Happa, Pavis, and Cities of the YK.
But its still a smaller market, which reduces the revenue. Conversely, writing a scenario is a complex affair; writing a setting book is more straightforward.