I think I may know, but I’m not positive:). Here’s some history. Our firm (Emergent Research) started do a U.S. coworking survey starting in 2008 with an estimate for 2007. Our counts for the U.S. for 2007 to 2010 can be found at: http://www.smallbizlabs.com/2010/09/over-250-us-coworking-facilities.html
In 2010 the Deskmag folks offered to do a global count. We were thrilled by this - both having global numbers and not having to do this ourselves - and we dropped our census to support theirs.
The numbers from the Wiki entry for 2007 and 2008 appear to be ours. They also appear to our U.S. only numbers - not global numbers. Please keep in mind back then there was very little hard data on coworking.
Way back in 2007 and 2008 coworking was mostly a U.S. thing, but it had started to pick up in other countries. So if I were to guesstimate (which is about all I think I can do) about the global numbers in 2007 to 2009, I would guesstimate:
2007 90 globally
2008 180 globally
2009 270 globally
Due to the recession, things slowed in 2009 and then started to speed up again in 2010. From 2010 on the Deskmag numbers are the best to use.