Why not use 64-bit Ubuntu?
11.04 is already available. But why 32bit is again recommended and what's "wrong" with x64 ?
P.S. I know about this question, but this is kinda different.
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I would think this recommendation is for those aren't aware otherwise.
I am not from Canonical, but I am thinking "32 bit" will work on all new PC's, "64 bit" won't. It would be bad if there was any form of fuss online if many people installed the reommended version, and have it not work correctly.
There are more 32-bit packages supported compared to the 64-bit set.
You might be interested in some history -- related to Ubuntu 10.04/10.10, Why not use 64-bit Ubuntu?
Guess, it is better to see a 'recommended' tag on 32-bit;