I don't know if there is any official etiquette, but yes if a blogger learns something from Flyertalk that isn't also posted in many other places it makes sense to me that the blogger should credit the source.

In this case, there was really a weird coincidence going on. I've been planning a Marriott triple dip post for quite a while (I have emails about it that date back to February 3rd). And, the day before I discovered your post, I outlined my triple dip blog post in my to-do list. I was really surprised about the coincidence when I saw what you had written.

So, given that background, should I have credited you/flyertalk? I certainly don't mind giving credit, but as explained above, I didn't think of it as something I learned from here. I'm curious what others think. Was there a faux pas here? What should I have done?