Fellow Pocket PC enthusiasts might remember the 32 processes limitation of Windows Mobile, where the underlying Windows CE kernel wasn't able to handle more than 32 simultaneous processes? Well, even if Windows Phone 7 is much newer and completely redesigned, it seems it comes with a similar limitation but this time it's not about background processes but notification limits. According to a blog post by Kevin Marshall, Windows Phone 7 can only have a total of 15 apps registered for push notifications. If a user installs 15 apps that use push notifications and a 16th app is installed, the user will get a "InvalidOperationException(Channel quota exceeded)" error message.
Furthermore, Marshall explained in his blog post: "My primary complaint is how the OS handles the user experience. No where does it tell the user how many apps are using push notifications and there is no central place to disable notifications for applications to free up a slot. Plus the certification guidelines only require that apps allow turning on / off toasts, not live tiles. So basically if an app is using a live tile, you need to uninstall it to free up a notification channel once you have 15 apps using them?"
It's yet not clear for me if this limitation applies to Live Tiles only but not to toast notifications or if it applies to all notifications - Live Tiles and toast notifications? In any case, it means that users might hit this limit pretty easy anyway. Live Tiles is the preferred method to keep users up-to-date, straight from the Start screen where Windows Phone 7 could notify - as long as it is supported by the application - about unread tweets, new Facebook statuses, weather forecasts, stock index, etc. On the first sight, a 15 apps limit seems to be reasonable (but only if the limitation applies to Live Tiles) but keeping in mind that the device itself is unable to generate notifications (by polling service statuses in the background) but relies on Live Tile and toast notifications it seems that 15 applications only is not enough
Cheers ~ Arne