An XFI-SFI interconnect runs up to 10.3 Gbps on a single serial link. It is double-pumped (bit on each end of the clock) so the clock rate is half that. This is the connection that links a 10Gbps phy to the transceiver module. You do have to keep the interconnects pretty short though.
XDR ram can transmit 8 bits per clock on a serial line: http://en.wikipedia.org/wiki/XDR_DRAM
Also, note how this is not a single serial 50 Gbps link - it's 4 parallel 12.5 Gbps links. You can run light in parallel with no interference, the trick is to make sure that each independent channel uses a different wavelength instead. So, they are doing it in parallel. Some 100 Gbps ethernet standards use 10 parallel 10Gbps lasers running at different wavelengths, but they are amazingly expensive because of this.
It is definitely not hundreds of times more - here, you can compare every manufacturer for the last 20 years.
Well, the Native Development Kit (NDK) lets you build native code. There is a regular C/Unix environment underneath. If you look at a project like the Android Scripting Environment, they've managed to make Python, Ruby and Lua work on the phone, packaged as an
You can compile pretty much anything for the phone, without needing root/Debian, though its not always as simple as 'apt-get install', for sure.
One way is to use the Native Development Kit, which lets you run regular C code on the phone. Here's a post explaining how to bind to bluez: http://blog.blackwhale.at/2009/08/android-bluetooth-on-steroids-with-the-ndk-and-bluez/
The other way is to use the existing android bluetooth API: http://code.google.com/p/android-bluetooth/
What that developer has done is use java reflection to wrap the existing (just not documented) android.bluetooth class API. I've been using it to communicate with an OBD-II adapter with some success (thought the dynamic port discovery API doesn't work entirely.)
For tethering, Wifi Tether works pretty well, since it doesn't even require the laptop to support bluetooth. It makes your phone a portable ad-hoc access point. Does require root access, for which there are some one-click solutions out there.
Many people are unenthusiastic about their work.