I have found that the bibliographies in my professional peer-reivewed print journals all follow the guidelines for the order as given in the standard style guides (Chicago, MLA, APA, etc.) : that is, in the alphabetical order of the surnames. However, in arXiv articles (which are not peer-reviewed but often end up as such elsewhere) I see a lot of reference lists which list the references in the order in which they appear in the text, without regard to alphabetical order. Is this only due to the difference between a bibliography and a reference list? I know that each journal has its own druthers, but is there any general standard among peer-reviewed journals?