As PR communicators we need to be very careful about content. PR people have a tendency to feel that if something is published then our goals have been achieved. The ease with which things can now be published undermines that presumption. The sheer volume of web content means that a lot of the stuff that appears on the net is of little interest to anyone other than the publisher. That which has no interest will have no impact.
There is simply too much out there and many sites and pages will quite literally never be viewed by anyone other than their originators. For print media cost is a barrier to entry for organisations wishing to act as publishers; there needs to be a sufficient audience in order to generate revenue to keep a publication afloat. What that has meant for PR people is that coverage, even in a niche publication would have some relevance and in almost every case we could quantify the circulation and readership and understand certain things about people who were reading the title.
We must not allow ourselves to be fooled that just because something appear on the web it has an audience. It is similar to the old argument that it is not sufficient simply to measure column inches. Fortunately there are a lot of tools at our disposal to measure what is going on on the web and the impact and authority of individual web spaces. Many are freely available. It is vital that we use them.