I think RIMs mistake is even trying to compete with Android and the iPhone. RIM makes business phones, that's all they make, and that's where they should focus. I don't recall any big companies switching their executives over to iPhones (Apple doesn't count). The reason is because RIM does the security that simply isn't an option with the iPhone or Android. Yes, their market share is hurting, but they're losing customers they never meant to appeal to in the first place.
Its like netbooks, when they were released, people bought them in droves, and other PC sales started to drop. People didn't need a full-sized computer just to browse the web, check email, or type up documents. Same with the iPad, it has started to cannibalize MacBook sales. When Intel released the Atom processor, it saw a drop in sales of other chips.
When something that better meets their needs comes along, people tend to switch. If the only vehicle out there was a Ford F-150 for $30k, and you needed a vehicle to get you to work in the morning, you'd buy a F-150. Now if Hyundai releases a $9k Accent that will drive you 10 miles to work and back on 1/5th the gas, you'd probably trade in for that.
Blackberries used to be the ONLY reliable smartphones out there (don't make me laugh with Win Mobile). Now that Android and the iPhone are out, many people are realizing they don't need encrypted communication or blackberry email. They never cared about the security, and they use Gmail or Yahoo Mail at home anyway. Unfortunately for RIM, it doesn't have a product to compete in the new market (who wants to drive a Ford focus?). That doesn't mean RIM will die, some people still need Blackberries, but it certainly will lose a lot of marketshare and will have to change its business strategy to survive (or be bought-out by HP, just like Palm, or by the government, just like GM).