Comment Allow Sideloading (Score 1) 210
The best way MS can increase the number of apps available on their platform is to allow Sideloading. Right now the biggest problem for a hobbyist developer is not the lack of dev tools (VS is one of the best dev platforms), but the fact that I cannot run an app I make on my phone without paying MS an annual fee.
Allow hobbyists to write and run apps on their phones, and they might create something which they feel can be sold on the app store, at which point you can start charging them for a dev license. But not many hobbyists will pay upfront to tinker with their phones which they already own.
Basically, make it easy for people to run apps on Windows phone, and you will automatically increase the number of available apps.