A ponnuki is worth thirty points
The proverb 'A Ponnuki in the center is worth thirty points' tells us that the ponnuki shape in this diagram is often very valuable.
Especially when played before middle game, a ponnuki in the center can exert influence in all directions. The number 30 here is of course just a manner of speaking - what is important is that it is large. One needs a very good reason to allow one's opponent to get one.
Even better than the ponnuki is the tortoise shell in this diagram, where two stones have been captured.
By analogy with the ponnuki proverb, some say that this shape is worth 60 points. Again, one should not take this number too literally, but whatever the value of this position is, it is huge.
-- Andre Engels
A match between Aoki Kikuyo and Wang Chenxing, white made a Ponnuki in center.
Alexandre Dinerchtein claims: sometimes ponnuki is only 29 points worth - when you make it without capturing the middle stone. See his GoSensations article:
http://gosensations.com/?id=2&server_id=5&new_id=226
Bill: Such a claim is unsophisticated. Does anybody think that the claim of 30 points for a ponnuki is precise? What is the difference between 30 points, more or less, and 29 points, more or less? ;)
A little later: I went to the site, and actually Dinerchtein asks if the "handmade ponnuki" is worth 29 points. It may have been a little joke. :)
John F. A little joke seems to allow a little pedantry - a handmade ponnuki can't exist. Nuki means capture. And actually ponnuki can be used of capturing more than one stone. It can be used for the turtleshell capture. It seems to be important to make this point because if you assume the capture of the enemy stone is actually a loss of a move by him, that stone alone is worth a lot more than 1 point.
MrTenuki: I would put the 29-point claim in the same category as "capturing a ponnuki is worth about 39 points."