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photo from crunchgear
I don't know of any survey on this (probably is since they survey any and everything) but I suspect most people now know how to pronounce Barack Obama.
BUT there is some software that does not - the new Kindle device from Amazon has text to speech built in but it doesn't know how to say his name.
I checked the text to speech ability of my mac mini and it does an good job on his name. Here's more on the CNN blog.
(hmm is Apple more liberal than Amazon? - better check the political contribution list)