A survey of college students (Head & Eisenberg, 2010) showed that wikipedia is widely used - but not exclusively:
Findings are reported from student focus groups and a large–scale survey about how and why students (enrolled at six different U.S. colleges) use Wikipedia during the course–related research process. A majority of respondents frequently used Wikipedia for background information, but less often than they used other common resources, such as course readings and Google. Architecture, engineering, and science majors were more likely to use Wikipedia for course–related research than respondents in other majors. The findings suggest Wikipedia is used in combination with other information resources. Wikipedia meets the needs of college students because it offers a mixture of coverage, currency, convenience, and comprehensibility in a world where credibility is less of a given or an expectation from today’s students.
Head, A. J. & Eisenberg, M.B, (2010) How today’s college students use Wikipedia. First Monday, 15(3), March 2010 for course–related research