executables cannot be run without root permissions, and then only after that executable has been saved to a folder. yes there are instances where people run all day long as root, for instance the eeepc has no sudoers file. the user can install apps with out password on the highly modified xandros stock os. as far as linux getting more popular, I think with all the different distros being run, it would be hard to write something that would infect more than one or two distros. I may be wrong on that, but it just seems logical.