Long story short, while making a blockchain crawler that would extract all ERC20 transactions I learned the hard way that ERC721 has the same "signature" as ERC20 (and probably many others that I haven't found out about yet).
However, when my crawler crashed on this cryptokitty transaction, I was puzzled ... turns out, when I look at the contract source code, the parameters of the Transfer event are not indexed at all, even though the actual ERC721 standard draft on github clearly defines them as indexed. After that, I randomly looked at some other ERC721 tokens, and some of them do not have indexed Transfer events either!
On the other hand I haven't yet seen ERC20 contract that doesn't have indexed parameters of the Transfer event yet.
Isn't this in violation of the standard ?
Is there any reason to it, other than making my life more difficult ;) ?