I never understood Unity’s low penetration until I published this web game and asked a friend to try it out, here is what she said:
"6:50
my computer says that this file can harm my computer… and asking if i’m sure i want to download webplayer-i386.dmg
it’s ok?
"
ugh, no solution to this one except maybe to have MS plug it into their OS 
right
he is a mac user obviously, otherwise he wouldn’t see the dmg file.
and the message is a normal one, thats the regular osx confirmation dialog you get for any file downloaded from the internet upon its first execution.
Also the unity webplayer is far from “low penetration”
the revolution browser plugin has a low penetration or potentially shiva, but definitely not unity.