Possibly one reason why people started spamming keywords is that they discovered that the so-called algorithms for recognizing synonyms and related terms don't work.  I can't remember which file or which terms were involved, but I tried once to minimize keywords in order to avoid rejection.  After the file was accepted I tried searching for it using synonymous or nearly synonymous terms and found that it didn't appear at all unless I used the exact keywords I had selected. Probably buyers are not always exactly precise in their searches so a little bit of looseness in keywording is called for.

This might explain why people would push the envelope a bit and add "screw" for what is technically a "bolt", in the above example.  In my case I simply added a few more keywords after the fact to conform with what I was sure were the common words which English speaking buyers would likely use.

However this doesn't explain the ludicrous keywords like "land vehicle", "business", "one object", "carpenter", etc. which were added to the picture of a pile of nuts and bolts.  I'm guessing that a buyer searching for those terms would be less than thrilled if a lot of junk like that cropped up.

I think it was Yuri who mentioned that his keywording is outsourced to India, then is polished in Australia.  Why don't the microstock agencies do that?  The contributors wouldn't need to specify any keywords, other than making suggestions and hints about pictures of obscure subjects or subtle concepts.   It would be a lot easier to train and motivate dedicated specialists whose living depends on accuracy and utility of their keywords, rather than trying to depend on content providers who (up to a point) will make more money the more they can spam keywords to get their images in front of more eyes, or on image inspectors whose expertise is in graphic arts and not language.

Or, they could continue to have the keywords added by contributors, but subject them to review by dedicated keyword polishers.  The contributors who require the fewest changes to their keywords would get a slightly higher commission because they cost the agency less money in making corrections.

You can probably find some more authoritative info out there, but a couple of tricks I picked up from advice given to amateur astronomers w.r.t. their telescopes and binoculars are:

1) Put the equipment into a tightly sealed plastic bag BEFORE bringing it inside, so that as it warms up, the moist air inside the building won't be able to condense on it.  When it has reached the temperature of the room then you can take it out, and no condensation will form.

2) Otherwise, when you bring it inside and condensation forms on it, be sure you DON'T put the equipment into a bag, box or anything, but leave it sitting out in a dust-free place, with lens caps, etc. OFF the equipment.  This way the condensation will evaporate as the equipment warms up to room temperature.  I would guess that it will take at least an hour or two for a heavy SLR camera with battery pack, etc. to warm up after being outside in freezing temperatures.

For optically perfect performance when outside in cold weather it is well known in astronomy circles that the equipment must be fully cooled to air temperature before use.  The warm equipment tends to make "heat waves" in the air, and the optical elements tend to be warped from the uneven temperatures causing contraction/expansion.  I would guess that for cameras, this is more true for large telephoto lenses than for smaller, compact lenses, but it's something to keep in mind.