The most basic difference between the interfaces of IRL and VR is that in Real Life, you are in the physical presence of the other person. Even though there is potential for deception in both Real Life and Virtual Reality, the Real Life situation has more advantages and ways to detect the deception. An important factor in communication, which Virtual Reality lacks, is that of body language. You can tell alot about a person by their body language and facial expressions, and in VR, the smileys just don't make the cut. In real life, there is the ability to engage with the physical person using all of your senses, and there is more reciprocation involved. Whether or not there should be types of warnings upon entering a MUD, MOO or IRC, I am not completely sure. It is common sense that these sort of encounters could easily be falsified and deceptive, so participants should keep that in the back of their mind and make good judgements accordingly.