Code:
$ bitcoind validateaddress 1AYSPTVt8WytG12Kz9guUpXjwAMFZG9CJh
{
"isvalid" : false
}
$ bitcoind validateaddress 1AYSPTVt8WytG12Kz9guUpXjeAMFb7AX2K
{
"isvalid" : false
}
{
"isvalid" : false
}
$ bitcoind validateaddress 1AYSPTVt8WytG12Kz9guUpXjeAMFb7AX2K
{
"isvalid" : false
}
The checksum in addresses is 4 bytes, so there is a one-in-four-billion chance that a random typo would get you a valid address.