As a referee, what should I do if I think the other reviewer of a paper is not objective? I was recently asked to referee a paper for a "moderate" but perfectly acceptable Elsevier journal, with an impact factor of around 1. The article in question was very poorly written, had several significant misconceptions in the introduction, but looked potentially quite interesting: I submitted a recommendation of major revisions, and included a list of fifty points ranging from the essentially (mathematical) grammatical to several significant scientific points. Frankly, I felt I was, if anything, quite generous -- rather than submitting a 2500 word review with a large number of salient criticisms, I would probably have been justified in recommendation rejection on the grounds that it was difficult to discern what had actually been undertaken. 

Recently, Elsevier made me aware that the other reviewer had submitted their comments on the paper. I was interested to see if they had agreed with my judgement -- and on which side of the accept/reject fence they had fallen. Much to my surprise, they had suggested outright acceptance, had written a very terse review which included details that were not originally in the paper, but could only be known to one of the authors [or their friends]. 

What should I do about this? I feel like having a badly-written one paragraph review recommending acceptance of a flawed article makes a whole mockery of the whole of peer review -- and additionally potentially means that Elsevier can't select reviewers appropriately.
My perspective as an Elsevier editor: This happens sometimes and is easy to see through. An outright "accept" on a first submission is so rare as to raise eyebrows in any case (at least, in my field). The editor has probably noticed the lack of thorough review by this referee and will give the review the appropriate weight (i.e. none). That said, I would not see any harm in emailing the editor if you are concerned, so long as you keep it polite and to the point.