Last week, Google announced that their Android market had reached the 10 billion download mark, a significant achievement that highlights the growing popularity of the smartphone medium. To celebrate this, a number of Android apps are available for only ten cents over the next ten days (At time of writing, the campaign has only four more days left, finishing on December 16th).

Now Apple have gatecrashed the party by announcing that there has been 18 million apps downloaded in their store overall, at a rate of 1 billion apps downloaded per month. From the Mac App Store alone, over 100 million apps have been downloaded in less than a year.

Both platforms highlight the massively growing and lucrative market that is the app store. While there are a mixture of free and premium apps to download and an ever growing platform (especially Android), it’s a market that will only continue to grow and grow over the coming months.

Chances are the 30 billion mark will be broken by either group within the next year or so. Perhaps the greatest worry is that Blackberry, Windows and Nokia are being left behind with the number of apps in both groups only reaching the hundred thousand mark at best.

While Blackberry has suffered from a number of self induced setbacks accumulating in the outage they experienced two months ago, Nokia are slowly building up their app store with Vision+ but it’s very unlikely that, with the grasp Apple and Google have on the market that they’ll leave much of a dent even if they get their act together.