lol I used to solomine litecoins with rpcallowip=*
I too thought that the worst that could happen would be for someone else to mine for me(don't think I forwarded the port on my router though) guess I got lucky.
With litecoin, there's no default rpc password. So unless you set the password to something like "password", you are not that vulnerable. Of course, it's still not totally safe to do rpcallowip=*.