Hey Antr, Jacob from SumAll here. Sorry to hear you had a bad experience with us. The tweets you're talking about that "spam" your accounts were most likely the performance tweets that you are free to toggle on and off. Here's how you can do that: https://support.sumall.com/customer/portal/articles/1378662-...
As the tweets contain both SumAll-related hash tags and Links to SumAll, this is definitely marketing that should be opt-in, not opt-out. Unless the user of your service is explicitly made aware of these automated tweets in clear terms when they sign up, this is a bit shady and dishonest to say the least.
And...? I'm sure it is. It markets their product at the expense of their user's credibility with their social circles. There's no downside! (For Sumall)
There is ... the ability for them to get word of mouth marketing is effectively dead for them. At best, if someone really likes it ..they no longer need to tell their friends... it's already done it for them.