I don’t know if this comes as a shock or surprise but iPod Touch 4G RAM is just 256 MB. This was confirmed by gruber on Twitter, saying:

Ways that the iPod Touch is crappier than iPhone 4:

• only 256 MB of RAM;
• non-IPS display;
• worse camera(s);
• no GPS;

This very much tells the difference. It still runs FaceTime and GameCenter though, things that poor iPhone 3G can’t run.