Nope.
In fact, this “non requirement” was reinforced with insights from a publicist friend who finds it an embarrassing practice to follow up TV, radio, and print media companies because it sounds too much like a hard sell, and on a personal level, downright annoying to the editorial team. You end up sounding like a wet market vendor or a stock broker at his game (not that I have anything against stock brokers or vendors). Going this far may even destroy sincere relationships, as they may have been made under false pretenses.
I like writing about the events I attend because it helps in the long tail end of things. Certain keywords are added to my site which I otherwise would not even have if I didn’t go to the event. Since blogs have unlimited real estate anyway and the cost of one post is really more about time spent writing, I say go and write about that fantastic event you went to.
Posting a block quoted press release isn’t the nicest of things to do though. It shows, a least for me, that the event wasn’t so great as it took someone else’s copywriting skills to create a canned writeup of the event. Press releases are tools for information and quality control, especially in print. But this is a blog, and being so, a free-er environment to express your thoughts about events that you attended.