My take after reading their web site is that Tiles only have GPS, and Bluetooth 4.
Using Bluetooth they communicate with the Tile App and also share info with each other. Then through the Tile App they upload all data to the "Tile Cloud". Users can only access their Tiles' data (location).
The only way to find a missing Tile is to be within 50-150 feet of it and activate it's beeper via Bluetooth. The "cloud" stored GPS coordinates will help get you it's last known location. Obviously it your tile is more than 150 feet (out of Bluetooth range) from your iPhone or any other Tile then it will remain lost as it has no way to communicate.
Sealed unit. You must buy a new one each year when the battery dies.
WiFi might be better, but most are WiFi's require passwords, plus the huge battery drain makes it impractical.
Might make an interesting study though to release some hidden in common objects (teddy bear, umbrella, etc) and see where they travel over a period of a year.