Looking over the comments on Geoff Pullum's recent post "Stupid less/fewer automatism at the WSJ", I see one point — implicit in many contributions, and explicit in a few — that deserves to be underlined with some empirical evidence. When a numerically-quantified plural noun phrase refers to an amount that may be fractionally divided (grams, seconds, meters, dollars, etc.), it's generally incorrect to follow it with or fewer rather than or less. And even when the counted units are not normally divisible, but are being considered as a mass-like quantity (points, votes, cents, items, soldiers), less may also be permitted or even preferred in formal writing.
Google Scholar indexes a wide range of scholarly, scientific, and technical sources, most of which are carefully edited. If we search Google Scholar for "grams or less", we get almost 5,000 hits — things like:
Intellectual and functional status at school entry of children who weighed 1000 grams or less at birth
It appears that for those passerine species weighing 22 grams or less, the lower critical temperature is commonly above 28°C
This cell was designed for samples of 20 grams or less …
In contrast, if we search for "grams or fewer", we get about 25 hits. Some of these strike me as flat-out ungrammatical, and were probably introduced by someone who had overdosed on bad usage manuals:
In a first aspect then, the invention is directed to a nut spread including nuts, and added vegetable oil, the nut spread having 3.5 grams or fewer of total adjusted carbohydrate per 2 tablespoon serving.
Others are merely awkward, or reflect a context in which people seem to be counting grams as indivisible units:
Each product contains six grams or fewer of net carbs per serving.
A main dish or meal must meet the 3 grams or fewer criterion per 100 grams and not derive more than 30 percent of calories from fat.
So if you're on a 2,000-calorie-a-day eating plan, then it should contain no more than 65 grams of fat, 20 grams or fewer of which are saturated fat.
It's worth noting that plural quantified noun phrases of this type often take singular verb agreement:
Ten seconds is a long enough period of time for TCP to ramp up new transfers to their full capacity.
BF3 is bubbled through a glass tube into the methanol until 125 grams is taken up.
The Cobb-Douglas specification suggests that 3.0 meters is also an important threshold in terms of public preferences.
As for things like votes and points, we can find plausible examples that go both ways, in approximately similar numbers, from well-written and well-edited sources like the New York Times:
The following gentlemen received 8 votes or less: …
… what would have been a disastrous night, considering how many House seats were decided by margins of 5000 votes or less.
in fully a quarter of the races, the difference between the two candidates was 1000 votes or less.
... 197 municipal elections this year had been decided by 100 or fewer votes, 74 by 25 votes or fewer and 15 by five votes or fewer.
Franck, Mozart, Rachrnaninoff, Haydn and Schumann, in that order, received 100 votes or fewer.
Several earlier unofficial recounts gave each candidate leads of 25 votes or fewer.
Six of the Chargers' games … have been decided by 5 points or less.
And the Broncos are 5-0 in games decided by 4 points or less.
It seems so because all six of Notre Dame's losses have come by 7 points or less.
The record was established in 1997, when 27.9 percent of regular-season games were decided by 3 points or fewer.
Seven of Cleveland's games have been decided by 7 points or fewer …
The 76ers have lost two games by 3 points or fewer …
And again, things likes points and votes often take singular verb agreement, when they are being considered as mass quantities:
“Sixty points is a lot” Llodra said …
… unless the danger is so extremely remote that 30 total points is too high a price to pay …
OPA wondered for a long time how to find out whether, for instance, 8 points is too much or too little for a can of peas.
The 40 points is the most ever scored against the Huskies at Gampel Pavilion.
At this stage of the game, 225 votes is a substantial margin.
60000 votes is a significant difference between the Democratic and Republican turnouts.
18,000,000 votes is more than any other man, living or dead, has ever received.
[Note that these points are emphasized in the treatment of less/fewer in Merriam-Webster's Dictionary of English Usage, as discussed here.]