Here's a series of infographics from the always informative Flowtown, showing the growth of social media ad spending. Currently half of the US$3.3 billion spent on social media ads worldwide is spent on Facebook. With Facebook now being the 500 million user gorilla, if anything I'm surprised it's not higher.

As a % of total media advertising, it will hit 12% of the total in 2011. No wonder so many media buying and planning agencies are (as I discovered in person on one occasion last week) are making an increasing play to manage clients' social media strategies - PR consultancies watch out.

Another interesting chart from the infographic, people who 'sometimes' (green % below) turn to social media when making purchase decisions. For travel it's 24%, clothes 23%, groceries 15%.

That might sound low in percentage terms but quantify that in absolute numbers. Facebook has 133 million users in the US and 28 million in the UK. If 23% of those occasionally consult their social media friends before buying clothes, that represents 30.59 million customers in the US and 6.44 million in the UK.

(The full Flowtown infographic can be found here)