It turns out that Janet Jackson was right; the best things in life are free. At least initially.

34 of the top grossing Apple iPhone apps are 'freemium' titles, that allow downloaders to purchase the full or extended versions from within the app, after they've sampled it.

The free model seems to be working well for developers, enticing users to part with cash after experiencing a taste of good quality content, rather than blindly slashing out on a full price app.

The top grossing free apps include Restaurant Store (#3), Tap Zoo (#4), NBA GameTime (#7), with a total of five apps appearing in the top ten and 20 in the top 50.

The freemium model has been a massive hit as 2010 has progressed, with only two such apps appearing in the top 50 back in January. It seems that try-before-you-buy apps could be the big app story of 2011.

Link: CNN Money