SFWA supports a site called "Writers beware," which tries to maintain warnings against literary scams. A recent post by Victoria Strauss to Writers beware is "Why Poets Should Not Seek Literary Agents"
"Beware, therefore, of literary agents whose guidelines indicate that they are looking to represent poets, or who put out calls for poetry collections. Be especially wary if a literary agency claims to specialize in poets. Nearly always, they’re either unscrupulous operators looking to charge a fee, or amateurs who know nothing about the realities of publishing. Even if they don't want to drain your bank account, it's likely that they have no track record of sales to paying publishers of any kind."
Yeah. Especially the part about "literary agencies that claim to specialize in poetry" (yes, believe it or not, there are some!) Give it the credibility test. Ya think they're really going to sell your book for so big an advance that they can make a profit on it? Really? Well, if it's not likely that they'll make a profit off the poetry publishers, just who do you think they're planning to make their money from?