Let me tackle these issues one at a time.
Its important to understand that all this work is done manually. Nothing is automated. This allows for the team to use their judgement on how to avoid what looks "spammy". When we post on any of these social networks, we usually take content right from your website. Sometimes just a short quote, sometimes an entire blog post and in the case of Pinterest, images.
Now before you jump up and scream "DUPLICATE CONTENT!" remember that the fine engineers at Google are not stupid, and they know that when links are shared on social networks, they will often quote or take content from the website. If Google didn't account for this, highly quoted websites such as the New York Times wouldn't rank for a damn thing.
The next point you brought up is the rate and structure. You are correct, since this is a monthly service all the signals you see on the site are delivered EVERY month. Then every additional month that you pay your bill grants you another set of signals. If you cancel, your signals stop. When i recommend that people stick to the plan, its because a natural drip doesn't stop after 30 days, it continues indefinitely...
I agree that its important to avoid spammyness in this day and age, which is precisely why you need a service like this. Compared to other systems and processes that use spun or repetitive content, this may be one of the least spammy methods you're going to find. The entire point of this system is to maintain a natural look.