TomTom shares fell 5.9 percent to $72.74 in Amsterdam, while Tele Atlas was flat at $32.42 -- well above TomTom's July offer price of $30.27.

The deal made strategic sense: It combined Europe's smaller, high-growth rivals to Chicago-based Navteq and Cayman Islands-based Garmin Ltd., the dominant players in the car navigation device and mapping markets.

TomTom would work closely with Tele Atlas -- its largest supplier -- to integrate Tele Atlas maps with its navigation devices.

But Nokia's $8.1 billion bid Monday for Navteq left investors wondering whether Garmin will now make a counterbid for Tele Atlas to stay in the running for mapping information -- or whether an even bigger player, like Google Inc., Yahoo Inc. or Microsoft Corp. might scoop up Tele Atlas.

Navteq and Tele Atlas are the only two providers of well-regarded mapping data measured at the street level around the world.

"They are unique assets," Pacific Crest Securities analyst David Niederman said of Tele Atlas and Navteq, though he cautioned against reading too much into this week's movement in share prices.

TomTom said it couldn't comment on whether it might need to sweeten its offer for Tele Atlas in order to get shareholders to tender shares. The company's formal tender offer launched Tuesday and will expire Dec. 4.

Tele Atlas and Navteq have both vowed to remain largely independent after they are purchased, selling their maps to all comers, Niederman said, adding that Garmin is "not forced to respond" to Nokia's move.

"It has not been part of Garmin's behavior pattern to date to make this kind of large acquisition," he said.

Despite Google's ever-increasing map offerings, he said he didn't think the search giant wants to get into the recording and routing of map data.

"That said, you never know," he cautioned, however.

Garmin shares slipped 0.9 percent Wednesday to $99.16 -- following a 10 percent tumble early in the week. Navteq shares have fallen to $75.97 because few observers believe Nokia will be challenged on its $78-per-share bid.

Niederman said Nokia's motivation to buy Navteq was not to shut out Garmin or any other mapmakers, but to be better able to steer its investments toward mapping areas that will be more profitable for Nokia.

In general, those are less focused on automobiles and more on pedestrian traffic; and in growth markets in Brazil, India and China, Niederman said.