Is it still possible to place classifieds in the NY Times? I don't think there's still anyway for someone to call up and have some random hash published, right?
I suspect the hardest part of doing that would be simply that you don't fit into their pre-existing categories.
FWIW, if you plan to do that, I'd suggest you put a Bitcoin block hash in the NY Times instead, which would prove the timestamps of everything that's been timestamped via Bitcoin. You can then timestamp your own stuff for free via OpenTimestamps, at which point your proof goes <your data> -> OpenTimestamps -> Bitcoin -> NY Times.
Timestamps are additive security, so it makes sense to publish them wisely. But if you're going to do that, might as well strengthen the security of as much stuff as possible in one go.