I've handled a lot of Cameo glass over the years -so I'm moderately comfortable around what is and is not fake -But you always have to be ready for whaever is coming next.....
At the moment I'd say the following.
The Standard reproduction Galle Cameo is pretty easy to spot -once you've handled enough and provided you stick to less outlandish pieces. As for the Japanese 70-80 pieces I've seen a lot that are very spottable-but I suppose there could be others getting missed. As with many fakes the best Japanese fakes I've seen were very big ticket items (£10,000+) -so safe for most pockets
Good Reproduction Daum Cameo is a little harder to spot -that can be scary -traditional shapes, colours and patterns are safe, but Daum were so diverse -its possible to get caught out if you are too bold!
Schneider Cameo fakes are better quality than the Galle, but still quite detectable -I still see these being passed off as correct.
Not seen much in the way of faked Legras. -not going to be big enough money -if they've gone that far they can just put a better name on it!
Much harder to detect is 'renaming' as I call it -ie someone takes an original Delatte cameo vase say worth £400 removes the Delatte cameo signature and adds a Galle signature. It's now apparantly 'original Galle' worth £1500. Even these are spottable with little practice -Cameo ones are easiest, but I've seen some so called first period (1890s) Enamelled Galle pieces priced at £10,000+ which I'm pretty sure were really £1,000 Baccarat pieces -but correctly dated.
Simple rule is: only buy if you are 100% sure or you can 100% trust the seller.
On a lighter note. I once bought a nice signed Legras, took it home, washed it, and to my horror the added signature came off. Distraught I gave it a second more careful wash -to see what I'd really bought- and revealed another correct Legras signature elswhere on the piece! phew!
cheers
Mike