“+1” is a convention that arose on the Apache Software Foundation mailing lists. The ASF still has the best, most functional process for mailing list based collaboration which has ever been evolved of which -1/0/+1 is only the thin wedge. (the whole vocabulary of
commit-then-review, etc is incredibly important when trying to implement a diversity of tactics over email, as we ran into time and time again with Indymedia). Worth exploring their process in depth.
Anyway, Google launched a “+1” product today, and there was some discussion as to where the “+1” convention came from. The first place I ever encountered it was this email from Rob Hartill, on Wed, 15 Mar 1995, as part of one of the early patch voting rounds on Apache 0.7.x (the Apache foundation having formed the previous month to turn NCSA httpd into Apache).
I'll use a vote of -1 have a problem with it 0 haven't tested it yet (failed to understand it or whatever) +1 tried it, liked it, have no problem with it.
Rob might have adapted it from an earlier source, but I’ve never seen it.