That's my theory, and what it is too....  Like the theory of the Brontasorus, which is thin at one end, much-much bigger in the middle, and thin again at the other end.

Song?
"Oh meee, oh myyy little turbines play well togtherrrr.
Looks like I'll neeeed a bigger inverrrterrr".
(I'm going out for "Idol" next time)

When an individual is investing in a small wind system (this could be that their building it themselves, or paying to have it engineered and installed), the money invested in the system, compared to how well it works is important. This is an important ratio to understand in the RE field. Most people call it "payback". Payback doesnt just have to do with money. It has to do with the amount of ENERGY it captures compared to how much ENERGY it took to produce the system.

It is common for people to confuse power and energy. It is not common however to get money confused. Usually money is important factor as well.

The multiple smaller turbines idea would take more energy to produce than one larger machine. I dont care how you look at it, it just does. Even if you got the materials for free, the work and energy put into building it will amount to more than it will take if you were to build one larger unit.  If you have to buy the materials, it becomes obvious.

Small turbines take MORE wind speed to move them. Their rotors sweep less area and therefore will not capture low winds efficiently. A large prop will however. You have to consider friction loss in all of the individual turbines, and the gaps in between their rotors, which is just wasted space because it serves no purpose. I suppose its similar to comparing it to the space between PV cells. Yeah they could put the cells up against each other, but the laminant on the back would not stick to the glass (and you probably would get some cell to cell arcing).

If anything less than 5 KW is not acceptable, then multiple turbines is not a good option since you are multiplying the probability of a failure.

multiple turbines will be more expensive.

multiple turbines will probably generate more power

               you have 5  1 KW Turbines             you  have 1  5 KW Turbine

   If one fails  at least  you will get 4 KW    vs    a failure means 0 KW

   if no wind at two locations  you get 3 KW    vs    no wind = 0 KW

You need to have all the multiple turbines operating independently and in parallel.

The multiple turbines should be matched at least in voltage so that all energy resources can more easily operate in parallel and be interchangeable.

Establishing a priority of resource utilzation will result in the most realistic "Green"

If it is very important to at least get some power under any condition, consider:

     Use multiple turbines +  multiple Photo Voltaic Panels  
 +   power stored in Batteries, hydrogen, etc.
 +   the Grid.
 +   Gasolene powered Generator

But a lot more noise! if they were all mounted close to each other.

But you need to come up with a cost-effective mounting of these multiple turbines.

Check the following link:

http://www.massmegawatts.com/

Hope that helps.

The only people out there I know of that are promoting the idea of lots of small wind turbines are the people who sell small wind turbines.  Look at any successful small wind installation and you'll see they usually have 1 turbine that suits their needs.  If its a decent turbine from a reputable company then down time should not be an issue (and if you're reallty worried about that get some PV and perhaps a diesel backup generator to get your through).

That said - I do know a few enthusiasts who do have multiple turbines, but usually they get one - then need a bit more and add another, or just get another because they're enthusiastic and have the land for it.  And these folks are not messing with tiny turbines like the air403 or such.