Relationships & Targeting are where the new rules of publicity equal the old rules.
I was amused by this post on a book pitch gone bad. The p.r. guy is arguing to an unhappy pitch recipient that he couldn't possibly personalize his pitch because he has so many thousands of targets.
Even in my father's day's in p.r. (1950s-80s), it didn't make sense to scattershot a pitch and it was critical to have relationships with writers, editors and producers.
In my youth I helped him select recipients of press releases, cut stencils and run the mimeograph, and stuffed, sealed and stamped the envelopes. I also listened to him on the phone. So I know his release list was always selective, and that he knew to some degree many of those on the list.
Now, with so many more media outlets than there were those decades ago, you need to be more selective, not less. Tailoring your approach will bring better initial results. And now, you have a chance to get "seconds" and "thirds" as your message is retweeted and reblogged.