Yes, you only need to enter your Twitter and Facebook login info once.

If you want the Thwapr app to remember your credentials (default) for Twitter and or Facebook, then you will be in good shape.

After entering your credentials the first time, you can freely post to Twitter and Facebook as many times as you want, never needing to re-enter your credentials.

Thwapr uses OAuth for Twitter and Facebook Connect for Facebook.

If you don't want the app to remember your credentials, you can also turn off that option in which case you will need to enter credentials every time.

You can also change your credentials and post to different accounts if you want.