Shares of Research In Motion plunged more than 22 per cent Friday as investors worried that the BlackBerry maker's new business model could end up hurting its lucrative service fee income and put pressure on margins.

The stock closed with a loss of $3.09 at $10.86 in heavy trading on the Toronto Stock Exchange.

After the market closed Thursday, RIM reported better than expected financial results, with a narrower loss and higher revenues than the market had been forecasting.

RIM said it had an adjusted net loss of 22 cents per share. The market had been expecting a loss of 35 cents per share. Revenue in the quarter came in at $2.73 billion US, slightly better than the expectation of $2.66 billion.

RIM 12-month TSX trading chart

But during a conference with analysts that followed the release of those results, CEO Thorsten Heins disclosed that RIM's service revenue model would change in the new year — evolving into a tiered plan that would allow business customers and casual smartphone users to pick their own service packages.

No specifics were revealed, but the mere possibility that RIM's stable service fee revenue might be jeopardized was enough to spook investors and analysts.

BMO Capital Markets analyst Tim Long said the changes to RIM's service revenue model invite greater risk.

"We have long viewed the recurring service revenues as the key value driver for the stock," he wrote in a client note.

"With subscribers declining, and the potential for a faster drop in average revenue per user, service revenues could fall even faster."

Heins moved to reassure investors in a Friday interview on the U.S. business TV channel CNBC. He said RIM's "service revenue isn't going away."

In its earnings release, the company said there would be "continued pressure" on its operating results as it prepares for the unveiling of its new BlackBerry 10 operating system on Jan. 30. It also warned that the imminent release of the new BB10 platform could also lead to a drop in sales of its existing BlackBerry 7 products, as some customers will likely choose to wait for the new phones.

Stock has been on wild ride

Before today's drop, RIM shares had been on quite a rally in the last few months as investors warmed to the idea that the new phones and platform would help the company claw back some of its lost market share in the competitive smartphone market.

The stock's recent low point came on Sept. 24, when it traded as low as $6.10.

While it is back in double digits, that rebound is of little comfort for long-term stockholders, who've watched their shares tumble from lofty levels above $140 four years ago.

RIM has struggled in recent years with flashier and more nimble competitors like Apple's iPhone and phones running Google's Android operating system. RIM's global share of the smartphone market plunged to just 4.2 per cent in the July-to-September quarter, according to market research firm Canalys.

The company is publicly optimistic that its BB10 platform, which is aimed at giving smartphone users a full multimedia experience, will be able to turn things around.

With files from The Canadian Press