Hmmm.. if you have been one of those contractors who have been bidding for singapore government projects, you will know how competitive the landscape is. And its a good thing for our Singapore government. Procurement is made simple and a lot cheaper by a simple bidding system. There is also a lot of accountability in the procurement process, making it a more honest system.
Surely, this should work well for the private sector too? Currently a lot of private sector sales go towards relationship building, etc… A lot of time is also spend sourcing for vendors, comparing codes, evaluating the different vendors. Even for us, when we need to say… print certain materials, we have to go hunting around many vendors to find one which we like…. Sometimes, I do wish we have a Gebiz to use… and I can just post my requirements… and get all those vendors to send me some proposals….
And to top it off, we have a great backend administration panel for us to rate the different offers and finally come out with a procurement decision objectively….. 
So less currying favour and more honest pricings. Surely.. this will be good for the shareholders of the private enterprises!
Is this one of your portal ideas?
Perhaps, you can talk to GeBiz (DSTA or MOF) on a PPP partnership to open up the platform for bidding within the private sector. I think you should have a good shot at it if you talk to the right persons.
Hmmm… even bakeries are using twitter… why not use it for my Gebiz idea?