I'm in the process of doing research for my computer science ph.d. project. Like many others, I'm using Google Scholar to find interesting papers for my research. Some papers are available through ACM and some through IEEE.
My university only has a subscription with ACM, not with IEEE, so it's free (for me) to read an ACM paper, while I have to pay to read or even download a citation of an IEEE paper. When I asked the faculty why we don't have an IEEE subscription, the answer was: Because it is really expensive. So what kind of papers do you think I'm looking at the most?
This makes me think: Will there eventually be a strong skew in the kinds of paper I'll end up citing? Many citations of ACM papers, none or few of IEEE papers? For now the answer is a definite yes. When I'm snowballing on a keyword, I now tend to close browser tabs with IEEE papers more often than ACM papers.
I have no doubts. This is a problem for science!