At the risk of sounding like a broken record, I'm going to agree with Magpie.
I've heard of agents claiming books they didn't have anything to do with, but I've never run across it. I Google authors after I find out which agent they've signed with. I just type: "(Author's Name) Author" in the search field and let Google do the rest. It gives you an idea what genre an unknown name writes in, and you often find a home page or Wikipedia article on them. This can sometimes verify who their agent is; I often use this technique for my comparison section in query letters. But your best bet is to hit P&E, the GLA, AAR and Publisher's Marketplace (on top of QT). If an agent only appears in one of those places (I've seen it happen), it generally (but not always) turns out to be a marginal agent or a scammer. There's also Writer's Beware, who are kind of like the secret police of writerdom. If you're suspicious about an agent, they can put your fears to rest or tell you they've got a file on them. They respond to professional emails and they really know their stuff.
The really good, supremely awesome news? With the exception of the GLA (
Guide to Literary Agents), these are all free, web-based sources. And even GLA has a webpage. You can really dig up a lot on an agent going through all these sites. If there's anything hinky about them, there will be red flags (and sometimes the absence of data is a red flag).
I also own several years worth of the GLA. Agents that appear in multiple years are generally safe, because the agencies that slip through their screening process are caught later on. (If you want to know how I know that, I can personal message you the details. I don't want to tell the whole tale here because it would take another paragraph and involves some specific agencies. Some of these scammer people are really vindictive, so I'm not going to state any names here.)
If you do find a scammer, let P&E and Writer's Beware know. And also let the source where you found the scammer know. Usually, they already have information on the agency or agent in question, but they'll appreciate the head's up. These "agents" thrive on secrecy. Silence is their best defense. If we can strip them of that, we'll all waste a little less time researching bad apples.
