Aside from getting them into the cloud or CDN business, it might also be useful to have a tangible deployment of Apple's enterprise technology, to keep AAPL in the minds of the executive crowd, now that traditional server vendors are dying out (SGI, Sun, etc.)
Beating a few benchmarks on performance, price or power-consumption is usually a good way to break into, or return to, a market.
Apple also has a rabid user base who will gobble up anything they put out.
Spending a billion just 'to keep AAPL in minds of the executive crowd' would be pretty dumb decision making and would put Apple right on the path of Sun.
This is not a bil in cash; they're most likely adding up the retail price of their own hardware sitting in warehouses and other stuff they can "license" to themselves for free.
If we say the cash cost to them is about half of that, I think 500 mil can be recouped selling their services to about 50 or so large corporations and governments.
Apple has cash to burn and it needs another business leg to hedge against its consumer offerings. 500 mil in R&D and insurance sounds about right. We will have to wait to hear what they tell their shareholders, in any event.
