As already reported by Chris Bensen in his blog, Micheal Swindell has reported some official figures of the size of the Delphi community. Over in the non.technical newsgroup (open his message dated 17 Aug, 20:46), CodeGear Product Manager shared numbers based on official surveys (and not on the internal company sales and registration data, which is a well-kept secret):

Delphi has a developer population of approx 1.75 million users worldwide in 2006. Delphi has 15% IDE marketshare overall (7.7% ranked out of 100%) and is the #2 Windows IDE and the #4 IDE overall.

There isn't much to add... If I could only sell a new book to one in a hundred, that will be 17 thousand copies!