Emilio Delgado López-Cózar, Nicolás Robinson-García, and Daniel Torres-Salinas have self-archived "Manipulating Google Scholar Citations and Google Scholar Metrics: Simple, Easy and Tempting" in arXiv.org.
Here's an excerpt:
The launch of Google Scholar Citations and Google Scholar Metrics may provoke a revolution in the research evaluation field as it places within every researchers reach tools that allow bibliometric measuring. In order to alert the research community over how easily one can manipulate the data and bibliometric indicators offered by Google's products we present an experiment in which we manipulate the Google Citations profiles of a research group through the creation of false documents that cite their documents, and consequently, the journals in which they have published modifying their H index. . . . We analyse the malicious effect this type of practices can cause to Google Scholar Citations and Google Scholar Metrics. Finally, we conclude with several deliberations over the effects these malpractices may have and the lack of control tools these tools offer.