Ben Peterson's HITs include "Rate Dating Profile Photos" for 8 different demographic groups (male or female, for 4 different age ranges, together covering all ages), "Rate Business Profile Photos", and "Rate Social Profile Photos". They've been posting since July 2013. Until on or about July 20, 2015, they previously had the following policy in the instructions section at the bottom of each HIT:
" Gender/Age Restrictions
For this HIT to yield useful results, we require that workers be of a specific gender and age group. We have intermittently available HIT groups for both males and females across all ages, so please find the proper one for you.
Workers submitting to multiple gender/age groups may have their submissions rejected. (Unless you actually changed ages; a one-time age group increase is allowed.) "
The requester mentioned on Reddit in March 2015 that until he could eventually be able to get a more automated system in place, he was handling people taking the wrong demographic's HITs by "running a script every month or so on my collected data to identify abusive workers and block them".
With that new system now in place as of July 20, 2015, this is the new policy. Also note that the age ranges for the dating HITs were changed at the same time (was 18-26, 27-37, 38-49, and 50+; now '25 & under', 26-37, 38-54, and 55+).
" Gender & Birth Year
You may skip this section if you have filled it out before. If in doubt, please fill it in again. If we do not have your data from a previous HIT or your answers are inconsistent then your work will be rejected.
Gender/Age Restrictions
DATING CATEGORY HITs have restrictions on worker gender and age as requested by the photo owner. We have intermittently available HIT groups for both males and females across all ages, so please find the proper one for you. "
There have been a few reports of people getting rejections/blocks for overlooking the new requirement to answer demographic questions. It says you only have to answer them once and can leave them unanswered on future HITs, but a few people think they might have been rejected on some due to not re-answering on those every time. By answering those questions every time (and always only doing the correct HIT group), so far I haven't run into such issues myself.
It seems it would be a good precaution to answer those questions on every one of his HITs, but that's a bit much for just three cents, so I made this script. It won't do anything until you edit the script's code to specify the answers that are accurate for you. I've tested it on the business HIT group, the social HIT group, my demographic's dating HIT group, and previews of several other dating HIT groups. Always take a quick look at what you're submitting before you do, in case he changes the HITs again in the future. And never submit a dating HIT for the wrong demographic group, the requester is serious about the consequences of doing that.
Screenshot of what one of the new HIT groups looks like by default (when this script is set up, it selects your answers in the part in the red oval):

See also: my MTG thread post
For many more MTurk-related userscripts, see the Turking Scripts set.