The boxing match billed as the "Fight of the Century" is over but the battle over smartphone video streaming of the Las Vegas showdown is just beginning.

Revelations that dozens of smartphone users streamed the Manny Pacquiao-Floyd Mayweather weekend fight have raised questions about how new technologies can get around copyright restrictions imposed at live venues such as sporting events and concerts.

There are no reliable figures, but thousands of people may have watched the fight via the Twitter-owned app Periscope, which allows any smartphone user to "broadcast" live video, and independent app Meerkat.