It can be done, but would need some work.  Content does need to have a valid owner, you could create a default user that becomes a default owner of everything, or you could have the site itself own everything.  You'd have to overwrite the logic for many of the actions.  Not trivial in scope, but certainly doable.

I would imagine with such a setup you'd be hit with spam *very* hard though...

Spam has certianly been an issue addressed. Do you beieve spam would arise if i do not market the website? I would simply just give the website URL to 30 business owners to use.

yep.

Anything is possible, but perhaps what you're asking is "has this been implemented already". My answer would be almost certainly no, at least not as an open-source plugin released on the community.

re: Evan`s remark - yep! discusions on topic of sms+elgg go back abt 3 years ! ;-)
they did have bi-directional (@then) $$sms gateways (@ the commercial elgg svcs )
you can always get yours $sms-thingy developed if some-1 will do it - along same lines
as was described by Marcus Povey (read backkk.. at those llinks)
here`s some bedtime reading :>

• http://community.elgg.org/discussion/view/119563/sms-enabled-elgg
• http://community.elgg.org/plugins/781727/0.0.1/paid-sms-%E2%80%94-registration
• http://community.elgg.org/discussion/view/203474/sms-how-to

You would need to create a new plugin and register these as menu items - see documentation. The menu you are looking for is 'extras'.

i tried and have so far failed... anyone know any plugins that does what im looking for?