A post on Arc [http://arcanesentiment.blogspot.com/2008/07/arc-gets-io-right.html]
made an excellent point - file modes are essentially exposing a low
level implementation detail for a high level feature. Would be nice to
have File.open_read, open_write and open_append (or less clunky names
if anyone can think them up; it's the principle of the thing) to
support the common cases.

martin