Yes it can.
The ipod touch 4g can video chat with an iphone 4 if you have a WiFi connection.
No, not like video chat on your email. But of you have the iPod Touch 4th generation you can use FaceTime, which is pretty much video chatting but the other person must have an iPhone 4, the 4th gen iPod touch, or a newer Mac with the FaceTime application.
You can text and even video chat if you have Skype. And yes you can call but it's illegal.
No
You Cannot Chat in Ipod Touch or Iphone only in a Ipad
With the free Skype app installed the iPod touch can do video chat on Skype. (See links below)
You can use FaceTime on a Mac to chat with an iPod Touch (See links below).
There are apps you can download like bluetooth IM which uses BlueTooth technology to send a message from ipod/ipad/iphone to ipod/ipd/iphone.
The iPod Touch can use FaceTime (See links below) to video chat with people on Macs.
The iPod Video does not exist, but look on the bright side. The iPod Touch now has two cameras! A front and rear, much like the iPhone 4.
FaceTime on the iPod Touch is using the camera on the iPod to have a video chat with another person with FaceTime for the iPod Touch or iPhone. You must have a Wi-Fi connection to initiate FaceTime, and the receiver also must have a Wi-Fi connection (or 3G connection for iPhones). It is good if you want to chat face-to-face without really being face-to-face.
I have added links to some useful software on the App Store that you can use to chat with other people using your iPhone, iPod touch, or iPad.