In my limited understanding it's the difference between the webkit engine that OS X provides to developers to use, as opposed to Chrome which probably does something different in that regard. Besides site-specific browsers, there are plenty of makeshift OS X tools that implement their own built in browser, and these applications do indeed share cookies with Safari.
The easiest way to test this is with Safari and any of the OS X site-specific browser or http debugging tools.
The Flash Player's "Shared Objects" (aka Flash cookies) are stored in a common directory, so the same Flash data is accessible from any browser (running as the same user). I do not believe Facebook's tracking is this nefarious, but the method would be quite easy to implement.
If one were interested in building something like this themselves or getting into the market, where would be a good place to start as far as acquiring hardware, learning about asic systems, and the software behind these systems?
I've been building my own managed firewall and router systems for awhile on commodity hardware, freebsd, and nice nics and would like to look into taking it to the next level and perhaps starting a business in this area.
The networking world is quickly moving away from custom silicon. Because of companies like Broadcom and Marvel it's getting easier and easier to buy/order ASICs instead of designing them. Cisco announced this year I think that all their lower-end switches will be using Broadcom.
So go check out what these 2 companies have in terms of switch on a chip type ASICs. AFAIK no one has come out with a multiport PCIx card that can do L3 switching between its ports. That would be neat. And I think it's just a matter of time till someone does. I would buy such a card if it worked under Linux or FreeBSD just to play with.