If you don't want the password argument to appear in ps/top listings, you can write over argv like curl does (see references to cleanarg(char*) in src/tool_getparam.c and the function definition in tool_paramhlp.c:133, at least in curl-7.26.0). I'm pretty sure that writable argv is guaranteed by C89, although that doesn't really mean anything in practice... but it works on Linux.
--Andrew Hills