The crowd-sourcing of pronunciations is already underway; unsurprisingly, it’s on Wikipedia. You an see it, for example, in the first line of the article on Reading: http://en.wikipedia.org/wiki/Reading,_Berkshire – anyone can edit Wikipedia, and I encourage interested parties to contribute there.
I’m about to suggest that we repeat it in Infoboxes (the info panels in articles, top right), so that it’s more easily machine readable, and can be made available via DBpedia http://en.wikipedia.org/wiki/DBpedia etc.
There is stalled proposal on OSM, to include phonetics: http://wiki.openstreetmap.org/wiki/Proposed_features/Phonetics – one issue is that the IPA character set isn’t unicode compatible. Suggestions for overcoming this are invited!
That aside, there is nothing to stop someone running a script to import IPA pronunciations from Wikipedia to OSM (or anything else); as it’s under an open licence. If someone does that, it would be cool if they’d complete the Wikipedia tag at the same time: http://wiki.openstreetmap.org/wiki/Key:wikipedia – we sorely need someone to run a script to do that.
A sanity check, that the Wikipedia article is the correct one for a place in OSM, can be done by checking the former’s coordinates and categories.