In recent years, there has been a great deal of interest in using social media and web 2.0 tools in educational and institutional contexts, especially in higher education. While some authors emphasize the great opportunities "which would be foolish to ignore" (Wheeler 2009, p. 4), skeptical voices point out that it is important to consider "the actual - rather than potential - use of Social Media in education" (Selwyn 2010, p. 3). So far the potential of these tools to support learning and teaching has been widely debated on a theoretical level. For example Guth & Petrucco (2009) argue that social media enable several opportunities for knowledge sharing beyond the classroom setting. Owen et al. (2006) and Ulrich et al. (2008) emphasize the facilitation of active participation. Beyond the theoretical discussions there is a large (and still growing) amount of empirical research dealing with the question of how educational institutions should integrate social media into educational practices (Berlanga et al. 2010, Meyer 2010). But by taking a closer look, it seems that most previous research has been limited to course evaluations or small-scale research projects. For these projects it seems difficult to point out implications beyond the boundaries of their own institution. However, so far little attention has been paid to conduct a research synthesis or a meta-analysis (Gouseti, 2010).

Taking this into account, the first aim - as part of a doctoral thesis -  is to create a clear picture of the actual use of social media in higher education settings. While this aim seems worthwhile, the actual methods to achieve this clear picture appear to be limited. For example by using the term meta-analysis as "statistical analysis of a large collection of analysis results form individual studies for the purpose of integrating the findings" (Glass 1976, p. 3), a lot of researchers (e.g. Eysenick 1978, Rost 2007) disagree on the method Glass suggested. At least studies with qualitative data from case studies or mixed methods approaches seem to be systematically excluded from meta-analysis. A question that needs to be addressed in this context is how could it be possible to do a systematic research synthesis or a meta-analysis using qualitative data? So the second aim of this paper is to critically examine the possibilities and the limits of research synthesis.

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