Today is the day that Greenfield Online Inc. [SRVY] has set for private equity firm Quadrangle Group LLC to meet or beat a $17.50, $460 million acquisition offer from an unnamed buyer.

Quadrangle in June reached an agreement to acquire the Internet surveying firm for $15.50, or $426 million, though that agreement allowed Greenfield to shop the company through Aug. 4. On Aug. 6 it announced it had received the new proposal, then indicated on Aug. 26 that it was superior to the Quadrangle deal, but gave the private equity firm until midnight tonight to respond.

The pursuit of Greenfield Online carries much intrigue, most pressing of course is whether Quadrangle try to top the current offer. Just for the hell of it, we put in a call to Quadrangle, but didn't reach anyone, though we don't  expect they would have divulged their intentions to a lowly blogger.

And while shareholders would like nothing more than a protracted bidding war to break out, if the ordeal were to end tonight the mystery of who the other bidder is would presumably be solved.

The only thing Greenfield has said about the prospective buyer is that it's a "Fortune 100 strategic buyer." Armed with this modicum of information, CL King analyst Jim Boyle went into detective mode in an attempt to out the bidder. He does about as well as could be expected, but fails to come up with a definitive answer.

As any good PI would do, Boyle first goes through the list of Fortune 100 companies and determines there weren't any market research or information firms, but several large media companies that could be involved. He notes that since the potential "crown jewel" of Greenfield Online could be its Ciao! Europe-based comparision shopping Web site with a social network aspect that just launched in the U.S., a media company could be logically attracted to a relatively smaller company with a fast-growing online asset.

The four media-related companies in the Fortune 100 are Time Warner Inc. [TWX], Walt Disney Co. [DIS], Comcast Corp. [CMCSA] and News Corp. [NWS]. Of the four, News Corp. has the highest profile online purchase with its MySpace buy in 2005. He also mentions General Electric Co. [GE], whose NBC Universal agreed to acquire the Weather Channel and its Web site last month.

Hopefully, these and other mysteries (like can Obama's team possibly pander to the Clintons any more than they already have) will be solved by tomorrow morning. -- David Shabelman

See Aug. 6 post from Tech Confidential
See Aug. 26 press release from Greenfield Online