Building will create employment, and keep the money in circulation which is the most important thing at the moment.

Awesome! One day, I'll have my floating island as well!
Let's not forget Ritchie Sowa's floating island made from recycled pop bottles. Much less than a cool $5 million, huh?
http://motherboard.vice.com/2010/6/17/this-guy-is-building-his-own-island-out-of-plastic-bottles-video

Cleaning up on land is easier then cleaning up on water. Yes these designs look amazing. Now plonk down ten thousand of them to form a village. They would be tightly clustered around land with resources as nobody wants to ride in their dinghy for 2 hours to get to shore.
How to deal with the many waste tanks, sewage and rubbish collection.
This is awesome as a holiday concept when there are just a few. An environmental disaster if multiplied by a few thousand.
Much better to have an entire floating city where access to land is a lot less urgent and waste management can be well organised.

a retired oil platform is a hell of alot cheaper to convert???

suprised they took so long coming
I thought the japanese would be making / buying these things by the thousands by now, I guess sea worthiness is an issue, some waves / storms may not be easy to avoid.
some may need to be able to be fold up like a flower and keep all ok while its fully dunked by a super wave and bob up later and "hatch" / bloom open again (hopefully with those inside ok.

It's as if no one has heard of houseboats or floating houses.

One Development that you did not mention along this line is New Utopia. This concept has been proposed for about 15 years as a monarchy as a government structure and not floating but raised platforms over an area that has already been declared a "country" by all international standards. The concept does not have the principal structure movable but there could be other such "floating islands" added within the governmental area.
Take a look at New Utopia as an alternative means of such living.

Guy is right on point, house boats have been around for a long time. They look fun but this not a new idea.

Freddy: Actually, New Utopia was mentioned, though only briefly.
The big problem I see with this in the long term is food delivery. Essentially this will have to operate like a small cruise ship: go into port, restock, go out to sea, go back into port. Also, the idea of wading or swimming around in deep water makes me a little nervous - I certainly would never think of taking my dog on a boat like this, even though the beach is one of her favorite places.
It could be interesting to set something up on an old oil platform to catch oceanic detritus and use it to slowly build a colony. Maybe some entrepreneurial Somalians will do just this.

What, has nobody heard of territorial waters and a 200 nautical mile exclusive economic zone? And are none of these planners aware of the International Maritime Organization and the thousands of regulations concerning any kind of vessel on the sea? What makes anyone imagine they can "moor" a city - or even float it - within 200 nautical miles of any land on the planet without full government authority? Create an independent, new kind of government? First of all, like what? Secondly, which existing government is going to approve it's location within their 200 nautical mile exclusive economic waters? And if the political and economic barriers are not enough to contend with the reality of a floating city in a hurricane would amuse CNN viewers for weeks. I have lived on a yacht for 35 years and finding a place where I can moor my vessel and then find land access for my 4.5m tender is physically a challenge - dealing with the legions of customs, quarantine, immigration, water police, local harbor rules and regulations and fees is a continual hassle.