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Steemit is not the Steem blockchain. Steemit could close tomorrow but that are tons of other apps on the blockchain that we could still use. Busy.org, Steepshot, D.tube. D.Sound, Utopian.io and more. This is the power of steem. It doesn't need 1 site or one particular use to be successful. Steemit can very well be replaced tomorrow and all our information would still be on the steem blockchain readily accessible.

So yes it's a good idea to build your business on the Steem blockchain, but you don't need to solely rely on Steemit. You could build your own app for your businesss that can access the steem blockchain for as long as the blockchain exists which could very well be longer than steemit.

As @nwjordan said, Steemit is not STEEM. You can learn more about that here: STEEM Is NOT Steemit. STEEM Is More Valuable Than Steemit.