People switch brands all the time as their needs and desires change. My first car was a Fiat 500, switched to a few Chevys, a Dodge, VW, and finally found and have settled with Toyota for the past 4 cars.
You really can't make a lifelong decision without living with the product for a significant time. Notning is perfect, so people will constantly be switching, not because what they have is no good, but because they want to try something different or see if it fits them better.
I never said that switching never happened, only that 94% of iPhone owners plan to buy another iPhone. That's pretty impressive and seems out of line with the number of folks in forum posts who claim that they switched or plan to switch. So either there is some demographic thing going on or some people just troll forums saying stuff like that.