The SAM it's intentionally designed for the purpose and gives very wanted effects to your iPhone such as making your battery life much longer - not experiences drainage after it's unlock with Ultrasn0w 2.1 - and getting the full benefit of push applications.
So here is the tutorial to activate iPhone officially without SIM card or Hacktivation:
1. Download Redsn0w 0.9.6b6, if you have not, according your platforms, download link for Mac, this one for Windows.
2. Jailbreak your iPhone using Redsn0w
3. When you've done with jailbreaking, now start Cydia, put this source url: http://repo.bingner.com as a repo in Cydia
4. Install “SAM” and “SAMPrefs”
5. Follow the steps in Troubleshooting/Hacktivated with redsn0w or PwnageTool
6. Go to Settings > SAM and touch “De-Activate iPhone”
7. Activate with iTunes when your iPhone is connected for iTunes to officially activate your iPhone.
If iTunes says invalid SIM, you will need to manually select the appropriate carrier under one of the methods besides “Automatic” and click on a SIMID.