Sending sms from tablet not allowed or not possible? This is more of a meta question, but the best place to ask I'm sure..

Why can't I send an sms from my samsung galaxy tab 10.1 3G tablet? Is it because the hardware does not support it (most likely), or because android 3.1 does not support it (least likely)?

Cheers!
The hardware and software support SMS, but not calling. The most likely explanation is that your contract is a data-only contract and SMS messaging is disabled by your operator. 

There is a chance, however, that the problem is your SMS settings. You can check these by opening Messaging, then open Settings from the top right corner and check that the Message center under Text message (SMS) settings is correct. The Message center number is network specific, so check it from another phone that uses the same network or ask your operator.