Last year they emailed quite a number of optimum members to join, they limited the number they accepted. They email links to do their surveys every few months. I did one yesterday, only 100 points, but that wasn't my point in joining, I like that I get to give my opinion on upcoming changes. For example one in November I think, asked about which coupons/promos you would prefer. Sure enough, the coupons changed a couple of months later.
The breast cancer one was a breast cancer awareness promo for everyone. You could enter your optimum number at the end to receive optimum points.
If they happen to email you to join, just move on it quickly, they fill up fast.