Hide webloc extension
The only thing I could find, suggested by Benjamin Schollnick, here., is this:


  find -x /path/to/folder -name *.webloc -exec chflags hidden {} +


It will hide the extension for existing files, therefore, you will need to run it again for newly created files.

Althought in the original question its said for Leopard, I guess it will work for Lion too.