From Wikipedia:
ResearchGate has been criticized for emailing unsolicited invitations to the coauthors of its users. These emails are written as if they were personally sent by the user, but they are sent automatically unless the user opts out, which causes some researchers to boycott the service because of this marketing tactic and contributes to the negative view of ResearchGate in the scientific community. ...
Several studies have looked at the RG score, for which details are not published. These studies concluded that the RG score was "intransparent and irreproducible", criticized the way it incorporates the journal impact factor into the user score, and suggested that it should "not be considered in the evaluation of academics". The results were confirmed in a second "response" study, which also found the score to depend mostly on journal impact factors. ...
Nature also reported that "Some of the apparent profiles on the site are not owned by real people, but are created automatically – and incompletely – by scraping details of people's affiliations, publication records and PDFs, if available, from around the web. That annoys researchers who do not want to be on the site, and who feel that the pages misrepresent them – especially when they discover that ResearchGate will not take down the pages when asked." ResearchGate uses a crawler to find PDF versions of articles on the homepages of authors and publishers. These are then presented as if they had been uploaded to the web site by the author: the PDF will be displayed embedded in a frame, and only the button label "External Download" indicates that the file was in fact not uploaded to ResearchGate.
