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It is a very good service, no need to trust, you can just subscribe and get yours posts boosted, check the website

It uses steemconnect or you can send yourself the transaction of 1 STEEM to @steembeem with memo subscribe
to get subscribed. While authorizing will allow steembeem to use your vote to boost/contribute help others subscribers posts (steembeem community) which makes you extra SP as posts curation reward shares/revenue!

But how do we know if the bot is a good curator? I don't want to be voting on any posts, only quality content.

i guess @steembeem should add in future a whitelist or blacklist to control for who's content you like usually (he should be as well within the subscribers list)