YES and NO.... yes if the file container is MP4 or AVI, no if the file container is MKV.
There is one great workaround that is a much better solution...
PS3 Media Server, this amazing freeware allows you to share a directory off of your PC or Mac and stream the content to your PS3 or crappy Xbox360. It will work with almost any file and will transcode on the fly if needed, that being said it works flawlessly with BLU-RAY rips downloaded from the net. I've watched 720p and 1080p MKV files with no problem. The odd time it won't play a file but there is a 2nd transcode option that the server creates. Also, make sure that your computer and PS3 are connected using Gigabit Ethernet and NOT wireless crap. If you go wireless expect delays playing music and video, also good luck fast forwarding or rewinding video content.
Enjoy!!!