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How do you get more steem power?
You invest money and turn it into SP.
You invest time making upvotes and creating content. Also placing those upvotes at the right time to ensure higher payouts of SP for the curator.
You invest time into developing relationships to gain delegations from users.
You create an incentive for many users to delegate SP to the account. Some form of interest generated from using the system.

That's true, but businesses can often get SP by other means, such as receiving delegations like how @steemhunt does.

That was more or less what I meant by investing in relationships. I haven't had the time to look at @steemhunt too closely how do they reward people who delegate to them?

They have created an SMT (currently and ERC20 token) that are distributed to everyone who delegates to them, as well as sharing curation rewards with them. People think the Steemhunt token might be worth something one day, so a lot of people delegated a rather big amount to them.