Some alt coins don't even bother making address validation, which is very irresponsible.
Users can easily send coins to a wrong chain, causing big trouble or even total loss. Case in point:
https://bitcointalk.org/index.php?topic=180518.0Bitcoin -- BTE -- TRC
I wonder if there are others.
Why including BTE on your list? You can't send BTE to a BTC (or any other) block chain address.
Are you positive on this? I am surprised.
I think having its own address validation should be made as a minimal requirement for any altchain dev.
You don't need your own address validation routine, it is already on the main Bitcoin code and with minimal tweak you can adapt it to your chain. Take a look on the base58.h file, the PUBKEY_ADDRESS constant is what rules if an address is compatible with your chain or not. If any other altcoin doesn't change it and has the same Bitcoin address format, then you are right, but that doesn't apply to us. Have you tried sending BTE to a BTC address or vice-versa? You should.
This is the output of the rpc console of the Bytecoin client when you try to send BTE to a BTC address:
> sendtoaddress 18as8p5DbgkhPihRcHrHNgc2uDkh4NH1vK 1
< Invalid Bitcoin address (code -5)