Actually, that's a misconception, at least in my case. It's not about being able to say you have one - it's about being able to keep up with the rigorous changes in the Android OS as a whole on the lightning speed that it is being updated. Think about it - when the DROID came out it was the debut of Eclair. Android 2.0. Now, we're debating if the Prime will come within 2 years of that same launch date with Ice Cream Sandwich 4.0
Since VZW folks (as I cannot speak for other carriers since I'm on VZW and have been for entirely too long) only get upgrades ~18-20 months, we only get subsidized phones at those time periods. Therefore, buying a dual core phone now is a bit of future proofing, as the trend on software is to always add more features - and that means a larger size. Couple with that fact is the fact that OS will tend to have support for multiple cores on par for when they start becoming mainstream, and if you buy a nice single core 1.5 GHz machine now, chance are that in 6 months to a year you'll be feeling the effects of a phone that simply is not fast enough b/c the latest Jubilee (or whatever J* is gonna be) will be optimized for dual / multiple core machines, and if you don't have one, then your phone could take potentially 50% more time in operations.
Now, some may argue that we're talking slices of milliseconds here - yes, but as I mentioned before, OSs tend to add features - and in doing so tend to get larger and larger. And this means hat your have more source code to process, more lines of execution. Sure, it may not mean anything when you're talking about a few lines here and there, but if you're talking 10000 lines of additional code, between 3 processes, which can only run sequentially on a single core machine, versus 3 process that can be split, so that processes 1and 3 run on core 0 and process 2 runs on core 1, then it makes a huge amount of difference. 10000 times, say .2 ms execution time difference = 2 seconds difference in execution. Then, add the sequential versus parallel operation, and you just added up to 3 seconds in execution in just these three processes. And Operating Systems are generally a lot more complex than 3 simple processes. In fact, most of our apps are generally more complex than just 3 processes as well.
The DROID was purported to be a killer phone - and it was, until Android evolved faster than it could keep up. WAAAAYYYY faster. 256 MB was way too small at the outset, and I'm betting that the 1 GB on the Bionic will be too small too soon as well.
Still, though, I'm going to get the BIONIC, then PRIME, and we'll see what happens to the BIONIC when I get the PRIME.
One thing is for sure - dual core is the absolute minimum I'm going to accept at the moment. Even if the naysayers argue that most apps cannot make use of a dual core app, that's not a problem - as long as the OS can, then it can automagically assign different apps to different cores, or the affinity, for those apps that only use a single core, and POOF! you can have two apps running side by side in a much faster manner than before. Or (and this is probably more likely the case) apps not meant to make use of both cores remain using only a single core, and the OS reserves the other core for itself so it can continue to perform background processes as needed, without slowing the phone and / or slowing the app down.
I've run into this argument thousands of times - "Why are you opting for so many cores, things cannot use them right now?" It's simple, really. To summarize what I wrote above - to make the transition smoother to when things can use them. Because, to me, it's all bout future proofing in order to be able to get maximum use out of my device.