The other day I was speaking to a neighbor, and he mentioned he was running a camp and had several kids signed up. His daughter piped up and said "I interested them in signing up", to which her father corrected her "You can't say 'I interested them'. Say 'I got them interested'".
I still haven't determined who was right. Clearly, there is an acceptable usage for the word interest as a verb: eg. for a waiter to say "Can I interest you folks in one of our desserts". Is saying "I interested them in buying a dessert," the same thing? On reflection, it does sound a little off, but I may be overthinking it.