The file browser filters out a few very common, generally HD movie format file extensions, .mts which is very common from HD mpeg4 vid cams and .m2v, .m2t both common from HD mpeg2 shooting vid cams. Could you add them please?

Also .avs, the AVISynth script file extension which blender via FFMPEG will load as if it were a movie, this allows certain preprossessing options to be done on the movie files by AVISynth as they are imported into blender. Very useful.

A link to explain. (Which will more useful when VSE proxies are reimplemented) ;-)

http://blendervse.wordpress.com/2010/07/11/preprocessing-proxies/

The .avs extension in more specific to MS Windows and you may feel not cross platform enough for default unfiltered.