The whole "exposure is never a real payment" thing reminds me of my old roommate who "paid" her friend in free haircuts for a logo. Two years later that friend was still tagging her in posts and asking for tweaks, like the free haircut covered endless changes. @karenwest has the right idea with the invoice and a due date, because once the file is out there you lose all your power. My roommate ended up just letting it go because chasing fifty bucks felt worse than the money. So yeah, if someone's already using your logo, the job is done and the bill stands. Why do people treat "I'll shout you out" like it pays rent?