NO bitcoin wallet can't copied or cloned. Because it is very unique wallet. So it is not so easy to cloned or copy bitcoin wallet.
I steal your wallet.dat file from your system.
Just install BITCOIND on a fresh machine, with YOUR wallet.dat file intact and bingo its MY wallet,if its encrypted, then I use jack-the-ripper to find the password on the wallet.
If somebody gains access to your wallet.dat file, then its theirs, this is why ppl have fire walls on their computer, or never run bitcoind with open ports