There is one advantage to using samba, namely if you want to hop around the video. Streaming requires buffering, while samba is more like having the drive attached.
I rather not have file sharing set up since that makes life easier for the hackers. That is why I prefer to stream my content on the lan, especially since the HTPC runs on windows.
Of course there is always the question of how robust the streaming software is regarding security, which it why I keep it on the local zone.
I did play with real time transcoding to stream music to my phone via cellular data. It works, but I really don't need that feature given how cheap SDHC/SDXC has become. On sale, we are talking 40 cents a gig.
I suppose if I had an iphone where flash costs are ridiculous, I might think differently about cloud services.