"Spontaneous collaboration can happen just as effectively with a remote staff, but you have to default all your channels of communication to digital ones."

So, if you handicap your local staff to use only a fraction of their communications capability then your remote ones are just as good?

Seriously - I've spent a large amount of time dealing with offshort staff and onshore staff, and staff both in the different buildings, the same building but different rooms, and staff in the same room - and having people sitting right next to each other makes a massive difference to the communication bandwidth.

The ability to turn your screen towards a co-worker, say "What do you think of that?" and get a reply three seconds later is _fantastic_ - and simply impossible with remote communications. (Where you can ping them on IM, wait for them to notice the message, start a screen-share, wait for them to accept, and then wave your cursor over the bit of screen you want them to pay attention to. It's effective, but it's nowhere near as fluid as pointing and handwaving.)