I just found this post via slashdot article. It seems that the popular internet telephony software - Skype reads your computers BIOS (whats that?) and Motherboard (huh?) serial number. This would have probably gone unnoticed. But someone tried running Skype on a 64 Bit version of Windows and ended up getting an error. So a curious programmer looked under the hood of the software to see what was happening - only to find it reading your bios and motherboard serial number.
It is not usual for softwares to do this. The last software who i know does this was Windows itself (not very surprising, i know!). Typically this information is used to generate a unique id for your machine when registering it with some sort of server - which is why Windows did it. They would use this data to uniquely relate your machine with your license of windows. However, why Skype chooses to do this is still a mystery.
But since this information can uniquely identify your machine across the world, this piece of news has created wide-spread annoyance with the on-line community.