Illegitimate companies and scammers have a simple objective. They're after your information in order to get your money. It's much more common for internet scammers to target hundreds of people for small sums rather than a single person for thousands. This is because demanding large sums for a product that is somewhat unclear is an obvious red flag to most.
Something unique that MyPoints offers that most other similar companies don't offer is the ability to earn cash back on some in-store purchases at select stores, along with their online paid surveys. Also, although their online store cashback rates aren't the highest in the industry (ironically, Swagbucks beats them on several offers), they do have special offers that other companies don't have, such as a bonus to sign up for Amazon Prime.
It’s a very well-known scam. You cash the check, then they ask you to either wire some of that money back to them as some sort of fee or buy something for them and send the item to them. So, you deposit the check, then wire some cash to them thinking that the check you just deposited will cover that. A few days later, after you already send them the money, the check will bounce and the money you send to them will come out of your own account.