I have a lot of legal concerns! Is this going to get me sued by my existing customers, whose details I would be sharing? Can you perhaps explain why this would be legal?
sure, it's just as legal as buying and selling email lists or other leads.
User privacy and legal matters will always be a controversial topic on the internet. Bitcoin for example challenged the government strongly early on, but now things have regulated themselves.
Pretty vague. Retargeting on what - Display/Facebook/Email? How would a customer onboard these lists?
Sure our startup will help you share everything that supports retargeting. You'd be able to share it through retargeting codes.
If you don't want to share the code you'd take it off of your website, that's a high level explanation.