Sounds like Yahoo thinks so. Starting in June, Yahoo will require that pay-per-click ads be 70 characters or fewer (currently, you have a long-copy option to include up to 190 characters).
It’s pretty much copying Google, but I love this. It makes you think more, and work smarter. How can you say the same thing in 70 characters and have it be just as effective as someting you would say in 190 characters?