Well, you learn something new every day. I just got a quick, informative summary from mikiegfla about the difference between blackout dates and capacity control. 
- See here: Numerous Hotels not accepting points And armed with that information, I found these threads also to be helpful:
- Re: there are no blackout dates??????
- Re: No Blackout dates doesn't mean when and where you want
- A Blackout by any other name is still a Blackout
- Re: Are you frustrated with the ability to redeem points for hotel stays?
I'm sure there's more, but I found it all to be rather informative.
Ultimately, it convinces me that I've been an unusually lucky (or, I guess, easy to please) Marriott customer for many (many) years. [I've even got one of those Marriott Marquis luggage tags to prove it: http://www.rewards-insiders.marriott.com/polls/1019] Fortunately, I've never been blacked out trying to use my points - ever.
Indeed, I'll never forget the time I was booking a week in Europe with my family at a nice hotel, only to learn that the week I wanted was eligible for a Points Saver rate - that's was awesome!!!!
All of which begs two questions:
- Have you had experience being blacked out (or constrained by a capacity control)? and
- If so, does your recent experience suggest that you are more likely to be blacked out (or constrained by a capacity control) today or it's still the luck of the draw?