Let's start with the basics.
Steem is the public blockchain which makes everything we talk below possible.
Steem is also the ecosystem, containing everything, from the blockchain, the decentralized applications (DApps) and tools built on it, as well as the users which organize themselves in various communities.
STEEM (often written all caps) is the base token of the Steem blockchain, alongside SBD (Steem Blockchain Dollars), both being the liquid tokens, and Steem Power (SP) as a non-liquid token.
Steemit is generally used with one of two meanings, none of which means Steem, as described above.
Steemit Inc. is a privately-owned company which has a high stake in the Steem blockchain. They also actively put a lot of work in developing the Steem blockchain and many other projects like Appbase, Hivemind and SMTs (and others they helped with). They also help some big (and usually awesome) projects with hefty delegations.
Steemit.com is a website developed by Steemit Inc. shortly after the Steem blockchain was created, with the purpose of becoming the first user-friendly front-end Dapp for the Steem blockchain, and showcase the possibilities that one can have by using this blockchain. It has never been a priority for Steemit Inc., after they launched it, as far as I read between the lines.
Now, why do I say we're harming Steem when we keep mixing Steem and Steemit in our posts and comments?
In fact, we probably harm Steemit Inc. too!
They want it or not, Steemit Inc.'s image starts with Steemit.com! That's what everyone sees when they look them up and see they have a website.
I, like many others, would strongly advice for a... more actual image.
I understand there are tight schedules and top priorities ahead.
In the meantime, Steem is not Steemit, and I think Steemit even wants to share more and more responsibilities of improving the blockchain with other willing parties.
So, we should just stop sending out the wrong message from inside and mixing at every other word Steem with Steemit.
I think it's not good for either of them. Not to mention, if we can't get our language straight inside the ecosystem, how can we expect an outsider to make any sense of this?
This is an even more stressing point with the coming SteemBlast proposed by on September 3rd. I've noticed Tim trying to emphasize on the distinction between Steem and Steemit on several occasions, when replying to comments, since the blast should be about Steem and not Steemit. Hopefully this message goes through eventually!