I know this is an old one but maybe allowing users to log in with Facebook or LinkedIn would be a happy middle ground - most people have one of these accounts already and those who can't be bothered to register a new system with a new password could simply log in with an email address and password they already have and you'd still be able to track info on who's reading articles.

This is a nuisance to me as I sometimes forward useful articles to colleagues who, although are in tech services, are not database people and refuse to join yet another forum so I have to copy and paste the articles into a word doc and email it to them so that they can benefit from the info.