Incorrect field detection — Google Scholar has problems identifying publications on the arXiv preprint server correctly. Interpunctuation characters in titles produce wrong search results, and authors are assigned to wrong papers, which leads to erroneous additional search results. Some search results are even given without any comprehensible reason.
Vulnerability to spam — Google Scholar is vulnerable to spam. Researchers from the University of California, Berkeley and Otto-von-Guericke University Magdeburgdemonstrated that citation counts on Google Scholar can be manipulated and complete non-sense articles created with SCIgen were indexed from Google Scholar. They concluded that citation counts from Google Scholar should only be used with care especially when used to calculate performance metrics such as the h-index or impact factor. Google Scholar started computing an h-index in 2012 with the advent of individual Scholar pages. Several downstream packages like Harzing's Publish or Perish also use its data. The practicality of manipulating h-index calculators by spoofing Google Scholar was demonstrated in 2010 by Cyril Labbe from Joseph Fourier University, who managed to rank "Ike Antkare" ahead of Albert Einstein by means of a large set of SCIgen-produced documents citing each other (effectively an academic link farm).