[mbesto]

Depending on where the company resides it's actually illegal do this.[1]

[1] - http://www.campaignmonitor.com/guides/permission/spam/

[petercooper]

It's not illegal in the US unless they don't provide opt-out and the various other things CAN-SPAM demands. That said, starring a repo could potentially be considered forming a relationship and relationship messages are exempt from those rules.