Yes, you can make it harder, if you have your DVD's replicated by a replication facility, you can specify that they be encrypted and protected with macrovision. Minimum replication costs (without encryption or macrovision) usually starts at around $1000 (USD). I think I remember reading that CSS encryption adds about $1 to the cost of each disk, so figure $2,000.

However, be aware that there are so many different software tools available that can descrypt and defeat the macrovision protection that all the encryption does is keep the honest people honest.