Got this today from Realwire, sounds like it would be worth signing up to:
An Inconvenient PR Truth - a campaign to reduce PR spam
Near the end of last year we carried out surveys with recipients of press releases which focused on the extent to which the releases they receive from the PR Industry as a whole are relevant to them. The results were quite startling with 78 per cent of press releases received by the participants being irrelevant to them. In addition more than half of them had taken action to block a sender of releases due to irrelevance.