Should SQL Server 2008 only be run on Server 2008 R2 (64 bit)?

Today I was told that SQL Server 2008 is supposed to be run on Server 2008 R2 (64 bit). Is this true? And if so, can anyone explain why?

Our development instances are running on 32-bit systems. I don't have any issue with migrating to 64-bit, but are there specific reasons why this is a preferred method?

From serverfault 8kb

• With x64 you get access to more RAM and CPU power than with an x86 OS and SQL Server version. You can use Server 2008 x64 as well.

  From mrdenny

• Whoever told you that is mistaken. SQL Server 2008 was released before Server 2008 R2, so how could it be intended to only run on Server 2008 R2?

  I think the issue that is being confused is that Microsoft strongly recommends the x64 version of SQL Server. They are pushing everyone to their x64 platform, so if you choose to install the x86 version of software, you may find yourself without an upgrade path in the future. This has nothing to do with Windows Server 2008 R2 other than the fact that it happens to only come in an x64 flavor.

  Farseeker : Well... the upgrade path would be to move to x64. The databases are completely interchangable between x86 and x64 platforms (not sure about IA64)

  MarkM : @Farseeker - Right, if you wish to upgrade the version of SQL in-place (not that I recommend that) and you are on an x86 OS, you are out of luck.

  Farseeker : @Mark, well yeah that's true. And you can't actually do an in-place upgrade from x86 to x64 so I guess in the strict sense of the word upgrade you're correct.

  MarkM : @Farseeker - Not that I would ever recommend it, but I've been consulting for some smaller shops on the side lately where resources are limited and some people actually have to do that kind of thing. Gross, I know.
  From MarkM