I did read that some researchers demonstrated that they were able to pick up the sounds from a hard disk seeking, and thus reconstruct data from the disk, even if the computer was not connected to the internet.
If what you and o_e_l_e_o are saying regarding data extraction is true (and I assume you both know what you are talking about), that would mean that open-source operating systems are equally vulnerable as close-source ones. It makes no difference what OS you are using when we are talking about extracting data from a computer's hard drive, for example.