The upgrade to firmware 3.1.1 makes me explore the original function of iPod touch without any 3rd party jailbroken applications.

This, should I say is a post about hide mature/adult/porn content in your iPod touch without using any 3rd party applications.
The trick is by enabling the restriction feature in your iPod touch and adding the appropriate ratings to the movie(s) you want to hide from public.

Enabling Restrictions Feature

Select General

Select General

Turns On Restriction

Turns On Restriction

Set Allowed Movie to G

Set Allowed Movie to G

To read more about the ratings, you can do so by following the link below.

http://www.motionpictureassociation.org/FlmRat_Ratings.asp

General Audiences

General Audiences

NC-17

NC-17

PG

PG

R

R

PG-13

PG-13

Tagging The Movie (.mp4) Files

Now the next step is to tag the movie (.mp4) files with the desired rating so it won’t comes out in the Videos menu.

Download Meta X for Windows software from the link below.

http://www.danhinsley.com/MetaX.htm

Use this software to tag your mature/explicit/porn movie to NC-17.

To View The Movie

Of course, first you need to add the movie to the library and sync your iPod touch with iTunes.

To view the NC-17 rated movie, simply go to restriction and change the movie settings to Allow All Movies.

Now you do not need to worry anymore! ;-)