Many off-the-shelf maps are just fine for stock cars or those with non-FI modifications (e.g. headers, intakes, E85, etc.). They can be used safely without putting your car on the dyno. Always read the tuner's build notes / read-me file to make sure your car "qualifies" for the map you want to install.
If you are going FI, you will need to have the car put on a dyno and mapped. That said, many retailers sell FI kits that provide a base off-the-shelf map that allows you to drive it to the dyno reasonably safely.
Tuners are able to modify large portions of engine maps by email depending on what you (and they) are trying to do. Map revisions don't necessarily require a new trip to the dyno.
You will always be better off having a car put on a dyno and specifically mapped to your setup, even if your setup is OEM stock and you are simply modifying the OEM stock map. But the gains may not be worth the price you pay.
Read this for ECUTek:
http://www.ft86club.com/forums/showthread.php?t=117520