If I post a poem, do I own it?

Good question! According to the current Terms of Service:

Our Services may display some content that does not belong to 7 Cups. This content is the sole responsibility of the individual who makes it available.

Therefore it is clear that an individual—you, for example—can make content available that is displayed by 7 Cups but does not belong to 7 Cups.

Later in the document, however, we find:

7 Cups shall retain all ownership rights in and to all content displayed on the Sites, including copies of data transferred or received by Member through the Sites.

This is clearly nonsense, and it contradicts what was said above. (I can only assume 7 Cups could not afford an actual lawyer.) For example, by displaying an English translation of the ancient Chinese poem 7 Cups of Tea, 7 Cups does not acquire "all ownership rights" to the poem, or to the translation. (It's not even clear that 7 Cups has the copyright holder's permission to publish the translation.) There are many, many more examples throughout the site.

I think maybe what it's trying to say is hinted at by the words "retain" and "copies"—that 7 Cups owns the particular copy of the content that is displayed on the site. Like if you buy a book you own that particular copy, yet you don't own the copyright. But it's written in a way that cannot possibly be taken seriously.

It's notable that it does not specifically say that by publishing content on 7 Cups you assign ownership of the content to 7 Cups.

It might be best, I suppose, to publish your poem somewhere else first with a date and a copyright notice in the standard format. Then publish a copy on 7 Cups noting that it is a copy of the original published at that other place, and perhaps including the copyright notice again. After that, you can do whatever you want with the one you originally published.

I don't think the type of content or where you put it on 7 Cups affects the situation.

@AffyAvo