Volunteers have been departing the project that bills itself as "the free encyclopedia that anyone can edit" faster than new ones have been joining, and the net losses have accelerated over the past year. In the first three months of 2009, the English-language Wikipedia suffered a net loss of more than 49,000 editors, compared to a net loss of 4,900 during the same period a year earlier, according to Spanish researcher Felipe Ortega, who analyzed Wikipedia's data on the editing histories of its more than three million active contributors in 10 languages.
Eight years after Wikipedia began with a goal to provide everyone in the world free access to "the sum of all human knowledge," the declines in participation have raised questions about the encyclopedia's ability to continue expanding its breadth and improving its accuracy.
Source: here