The iOS App Store is large and dynamic market place, and measuring its size can be tricky

Source: 148apps.biz

On Sept. 1, Steve Jobs announced that there were more than 250,000 apps to choose from in Apple's (AAPL) App Store.

On Saturday, two websites -- VentureBeat and MacNN, it's not clear which was first -- reported that the count had crossed the 300,000 mark.

Fifty thousand new apps in the space of six weeks? That would be unprecedented -- if it were true.

It turns out, VentureBeat and MacNN have made a rookie mistake. They're using a number from Mobclix, an ad exchange network that knows on which apps its ads have appeared, but not whether those apps are still available for download.

More