A senior investment banker at a major Wall Street firm kept sending out e-mails on his BlackBerry on Wednesday morning. And they kept bouncing back.

It's one of those things -- you don't realize how important it is to breathe, until you can't do it, said the New York-based banker, who declined to be named because he was not authorized to speak about the subject on behalf of his bank.

The banker is one of millions of BlackBerry users in various regions around the world who have been plagued by service disruptions over the last three days, with North American users of Research in Motion's popular handheld device being the latest to get hit on Wednesday.

Wall Street honchos and others who tend to spend more time on their BlackBerry than perhaps with their families were left frustrated at the service disruption.

The sentiment may prompt more banks and law firms to start using rivals such as Apple's iPhone and Google's Android-based devices -- a move that would not bode well for Research in Motion, which is already losing market share.

Law firm DLA Piper, which has 4,200 lawyers worldwide, is accelerating discussions about making a switch to iPhones and Android devices, said Don Jaycox, chief information officer.

This has brought it to the front-burner, Jaycox said. It will cause more people to opt for other choices.

It would join several Wall Street banks that already allow employees to use other devices to connect to company networks.

Credit Suisse earlier this year started allowing bankers and other employees to use their Apple and Android devices on the company network. Barclays Capital allows some employees to use iPhones and iPads. Standard Chartered switched from BlackBerry to iPhones for many users several months ago.

At Sagent Advisors, an independent investment bank in New York, 10 percent to 15 percent of the users have switched to iPhones, while a similar number have taken up Android devices.

It is still mostly BlackBerry but quickly moving away, said Terrence Barron, Sagent's head of marketing and communications. Over time there has been much more of sliding over to Android devices and iPhones for us.

Research in Motion advised clients of the outage in the Americas and said it was working to restore services. The company wasn't immediately available to comment on this article.

The switch away from BlackBerry comes as more employees demand to be allowed to use their iPhones, iPads and other smart phones on company networks. Some do not want to carry two devices, and some prefer tablets such as iPads over laptops.

One of BlackBerry's main selling points -- Research in Motion's top-tier security features -- is also no longer unique.

Mobile device management companies such as Good Technology and MobileIron are offering alternatives that are making it possible for banks and other firms to make the switch.

Banks also have an incentive in allowing employees to use their own devices, as it can save on what the company has to pay for the BlackBerry service plan.

Credit Suisse, for instance, has seen about one-third of its 25,000 BlackBerry users switch to Apple or Android devices this year, saving the bank millions of dollars, said Stephen Hilton, the bank's global head of technology infrastructure services.

The bank even offered employees a rebate to pay termination fees on existing BlackBerry contracts to make the switch.

We are seeing very rapid adoption of this 'consumer technology' platform, Hilton said. I suspect this (outage) would be another reason why people may reconsider at refresh what device they buy.

'REAL PAIN'

The disruption on Wednesday left many bankers at a loss.

I rely on BlackBerry and these outages have been a real pain, said a senior M&A banker at the London office of an international bank, who requested anonymity because he was not authorized to speak to the media.

A Houston-based investment banker who focuses on the energy sector deals said he copied himself on an email to make sure it went through.

A colleague who was traveling, he said, called from the road in panic because he had not received any emails for a couple of hours.

But while the disruption was frustrating, the banker said they had not been frequent enough to force a change at his firm. The last big outage in North America happened two years ago.

If BlackBerry were down every other day it would be a pretty big issue, the banker said. It just forces you to actually call your assistant. It's like the old days, when you had to talk to people.

(Reporting by Paritosh Bansal and Leigh Jones in New York and Victoria Howley in London; Additional reporting by Michael Erman and Soyoung Kim; Editing by Bernard Orr)

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