I was on another forum and they were telling their members that the correct way to write poetry now is not to capitalize the beginning of each line, but only capitalize the poem in the same places you would if it was prose.

Has anyone here ever heard of this, and what do you think about it?

I'm dubious of anyone saying that anything is "the correct way to write poetry," or worse "the correct way to write poetry now." After all, as Kipling put it in one of his poems,

"There are nine and sixty ways of constructing tribal lays
And every single one of them is right!"

And even to the extent that I would say there are definite rules to poetry, for every rule there have been at least a handful of poets who have disregarded it with good reason (and dozens if not hundreds who have followed suit for what were not good reasons, sigh ...). Look at e. e. cummings, for example; his capitalization, grammar, and diction, were ... unique, to say the least, but many of his poems follow the rules of one traditional form or another (especially the sonnet form) fairly strictly.

But on this particular question: I've been dithering for a while about whether I ought to (in preparing a collection of my poetry for self-publication) make this very change. Each side has its benefits: If you capitalize each line, that's a visual indicator (not necessarily a reliable indicator, but an indicator nonetheless) that you haven't simply taken a block of prose and broken it up into lines to call it "poetry." But if you only capitalize the beginnings of sentences (and proper nouns, etc.), that encourages readers to read it "properly," rather than reading one line, pausing, and starting up the next as if it were a new thought. (And, to me, with poetry how it is read or spoken aloud is far more important than typography and such.)

I recently heard this rule in my Creative Writing class. We didn't go that far into detail, though, since it wasn't specifically a poetry class.

I sometimes write poetry that way, and sometimes other ways. It just depends on what fits the poem.

In Poetry, just as in Prose, there are many different genres and styles, and that's always a good thing. How one writer does it is naturally different from how any other writer does. Saying that something is the 'right' or 'wrong' way doesn't seem accurate. Especially if it's a dated thing: Such as it NOW being correct to not capitalize the first lines.

I do, most of the time when I'm writing poetry. I think it makes the poem look more finished, concise, professional. The only time I would, on a personal level, even consider not capitalizing would be in what they call 'free verse'. Whether or not this is technically accurate is up to my editor, I suppose.