Why is this a problem for Mozilla but not a problem for VLC?
I've found the VLC firefox plugin more stable than flash, downsides being it doesn't always get detected by javascript feature tests and UI integration isn't the greatest.
Some people claim the situation of H.264 patents in Europe isn't that clear, though. VLC might be just benefiting from a lack of initiative from patent holders.
VLC have no money, so there's little incentive for H.264 patent holders to pursue them. Given that fact, the game theory suggests it is in the H.264 patent holders ultimate interests to allow VLC to be distributed far and wide. That provides an avenue for further penetration of H.264, which may create additional opportunities where royalties can be sought.