It's to prevent unwanted taps. I know that I have hit links while browsing on accident with my iPhone, accidentally hit next when i didn't want to. It's a nice feature, although it would have been nice if RIM gave users the option to disable it.
I don't have to double-tap to confirm anything, unless a separate prompt comes up. Single-tap works just fine. I haven't futzed with the tap settings at all yet, either. Definitely check your settings.
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