Geniatech actively monitors for leaked keys. If you find a list of 100 keys on a blog, they have already been blacklisted. The software will activate but then "phone home" within 24 hours and disable itself.
Use official upgrade or migration options Eyetv 4 Activation Key
If you paid for a key but EyeTV 4 rejects it, try these steps: Geniatech actively monitors for leaked keys