San Jose Mercury News, Calif., Peter Delevett Column.

Byline: Peter Delevett

Apr. 3--The stock market may be down, but there's still a bull market for April Fool's jokes.

Exhibit A: a press release issued Friday by online community Craigslist.org. The release claimed that list founder Craig Newmark was, in fact, a fictional character along the lines of Betty Crocker and was being discontinued "in a cost-cutting move."

"Recent `Craig' sightings are reputed to have been paid appearances by Jason Alexander," better known as "Seinfeld" icon George Costanza, the release added.

The bogus billet caused some hand-wringing from some of the site's users, reports the real Newmark, but most folks seemed to catch on quickly that it was a joke.

Some readers of Red Herring weren't so swift. When the magazine's April 2 issue hit newsstands …