Consumers and business workers are flocking to Research in Motion's BlackBerry service despite recent embarrassing glitches that have shut down service for hours on a few occasions.

Research In Motion on Thursday boosted its forecast for subscriber account additions in its fiscal fourth quarter, which ends on March 1. Back in December, RIM predicted 1.82 million new accounts, but now it expects that number to be higher by 15 per cent to 20 per cent. That will mean a total of about 14 million subscriber accounts at the end of the quarter. Final results will be revealed on April 2. The company's revenue and profit forecast hasn't changed.

The company raised its forecast during a difficult month. Last week, BlackBerry users in North America lost the mobile email and data service for about three hours in an incident RIM blamed on recent upgrades to an internal routing system. Then, some North American users reported the service down on Wednesday morning this week. RIM said scheduled maintenance slowed down delivery of some customers' email. (Another outage in late January was caused by the AT&T Wireless network.)

BlackBerry has suffered from major outages before, namely last April in North America that lasted overnight. In 2006, users lived for several months in fear of a service shutdown in the US sought by NTP, which sued RIM alleging patent infringement. RIM eventually settled the suit in March 2006, agreeing to pay more than $600m.

The problems shone a spotlight on RIM's reliance on a proprietary architecture and the fact that all messages have to go through its network operations center (NOC). These factors could make RIM vulnerable to a single point of failure, some analysts said. But in reality, BlackBerry devices probably aren't any less dependable than mobile email systems from other vendors, such as Microsoft, Palm and Nokia's Intellisync, they said.

BlackBerry service can be managed through a BlackBerry Enterprise Server within an organisation, but RIM is now making a push for consumers with its BlackBerry Internet Service, which can be ordered from a carrier.