As a reviewer I routinely search for the paper title, basic paper keywords, and/or the particular combination of authors' names in an academic search engine. This typically shows the close environment of peers, a sub-sub-area, so to say.
But not once or twice this has resulted in rather unexpected results, such as a very similar titled paper with paragraph-wise text overlap and an author subset/superset.
This greatly saves my work time, because in the above case I can immediately flag it as plagiarism, send my review with snarky remarks to the editor, and go back to whatever I did before reviewing. I have yet to encounter a true double submission, but my actions would bear a strong degree of similarity.
(You notice by now some degree of irony here, but I really have seen such plagiarism cases as a reviewer.)