Whilst I agree it's strange to wait x amount of time before realising a key is fraudulent, it's about time someone cracked down on these shady key sites. There's so many of them now most of which have next to zero customer service and shady practices - what are Ubisoft meant to do? Oh they stole a load of cd keys but nevermind..? There are legit licensed key resellers who have great prices such as GMG, getgamesgo, humblestore etc etc and are unaffected by these bans.
GMG, GGG, etc, tend to have the same/ similar prices as Steam. None of them are any good unless there's a sale on. The regular prices are just naff.
As for the grey market, don't Ubi region-lock their games? I thought they did.