And how many are there, and why don't more people give more of them, and....
HoundDog asked the question in April, and it took me this long to a) come up with a way to answer it, and b) be willing to tackle the data. In the end, I settled for one month's information, and tried several ways of parsing it.
The top 1% of all comments (which are primarily tip jars and first comments) collect 13% of all recommends - just under 250,000 of them.
81.9% of all comments manage to get one or more recommends, 67% get two or more, and over half - 56% - get three or more. 15 recs puts a comment in the top 10%.
Average recs/day - 56,400. Some users never recommend, some manage to treat every diary they're in as though it were Mojo Friday. And there's no simple way to check how many recommends users give, so the following is purely SWAG (Swinging Wild-Assed Guess). Assuming that the recommends per user follows the same general curve that's been ubiquitous in the other analysis I've been doing, the median number of recs per user will be about 3, and the average will be between 3 and 6 recommends per day. That means something like 10-15,000 users doing their bit on any given day. If you manage upwards of 20 recs - hey, top 10%, and consider this a pat on the back.