Quite. And the range of such parasitic plants is amazingly large and the way in which they feed is too.  Some are critically dependent on other plants for food and have practically no stored food even in their seeds (like Striga, witchweed, growing on the roots of grains), whereas others, like the Australian "Christmas Tree" (Nuytsia) look innocently normal, but parasitise the roots of plants many metres away. 

You might argue that this is not the same as eating plants, but it does feed the culprit, and it sometimes kills the host. Sounds like "eating" to me!

Yum!

Jon