|Readyboost is not known to many people and not all people can use it. |
It is a great way to speed up Windows 7 systems if you tend to open a lot of files. And who doesn't? A mobile user could use an expresscard or other flash to help prevent the dangerous usb sticking out.
I can't say any reason not to use it as long as you don't bump or damage it and that would be true for any cord or connector or such.
It speeds up your system, try it.
Why did it take me over a year to phone in a problem to ATT?