In 1998-2002, Blackberries really were the peak of ease of use and efficient communication/calendar management. Every executive/financial trader/beltway insider had one. The early 800/900 series Blackberry were like the iPhone of 2007.

In 2007 the iPhone was seen as an oddity by those who used their blackberries for business - without a keyboard, and really rudimentary communication tools, it wasn't ready for real-time business communication. But wow - that browser, and maps app was something else; and then Apple let third parties develop applications for the iPhone...

By 2009, after a couple iterations of the iPhone, I was running a network engineering team, and provided everyone on the team a blackberry so they could communicate real time with each other (We had a corporate BES server). Every single one of them was left in a desk drawer, as people ignored them and just connected their iPhone to their iMap account and used SMS for the real time stuff.

I just got back from a 4 week engagement in Singapore, and I was working daily with fifteen people in five organizations across four companies, distributed across three sites and field visits. We had to perform real-time communication during some particularly tricky diagnostic event on hardware, at the same time we were tracking some configuration remediation in a meter-lab. Every single person present (except for one poor Field Engineering manager from California who showed up with a non-GSM android) kept in touch with WhatsApp. We didn't even have to supply the four college students we hired to do some field-evaluations with phones - they showed up with their own devices (all Androids), and we simply added their accounts to our group chat system. Latency was on the order of a second even with Singapore's surprisingly iffy data environment (at least from the perspective of my California AT&T iPhone)

I think a major contributor to the death of blackberry was a combination of iMap ports open to the internet + Exchange Support in iPhone + awesome replacements for BBMS (inexpensive SMS, Viber, Whatsapp, etc...) - every key advantage of the Black Berry, with the exception of that keyboard, has an equivalent or better replacement today on the Android/IOS platform, with the addition of a world class app suite that's available on the Android/iPhone, but will never, ever, come to the Blackberry (except in the form of Android sideloading - but that further kills the need to develop blackberry specific apps)

That's what killed the Blackberry.