It is easy to hide, avoid, procrastinate, give excuses when you are online. You just select to be invisible or block selected people from viewing you. You can choose not to reply, or to reply with words that are vague for instance. You can say you missed the email or did not receive it at all if confronted. Maybe it went into your spam box, which you don't check, by mistake. You can avoid issues and confrontations simply by keeping quiet and ignoring.
You can also use pseudonyms for email addresses or fake identities in chatboxes or social networking sites. You can change your identity, and become someone else without anyone knowing. Seems like anyone can do anything these days online. People can hack, steal others' identities, blackmail, cheat, spam, learn how to make a bomb, spread viruses etc
We are living in dangerous times...
I think I've been watching too much Criminal Minds and marveling at Penelope Garcia's tech abilities!