Is there any evidence of that aside from abject whining?
Nobody's used the thing yet to say one way or the other, but if it's responsive and functional at 256MB, then there's no issue. It's no better than pissing matches over engine horsepower, the wattage ratings of electric power tools, or CPU speed.
There's such a thing as diminishing returns.
Yes, I'm sure the clueless Internet hordes will really inspire shame in engineers, designers, and programmers involved in making the thing.
I have to admit, they have a point if there are issues w/ the iPad related to too little memory.