Louis Gray precisely describes what goes on when multiple blogs announce the same product at roughly the same time: Why the Embargo Process Is Broken and Why We Still Need It. He writes:
Why would media/press/bloggers agree to an embargo?
1. If they wouldn't agree, the company might not give them the story.
2. Because an embargo often comes with news ahead of time, allowing time for writing.
3. The service might have given them an interesting non-standard angle.
It's a worthwhile read if you want to know a bit about what goes on behind the scenes at a publication like upFront.eZine.