A couple of weeks ago, a thread began at Absolute Write about a new and as-yet unproved agent. Said agent rocked up; questions were asked; a magnificent bun-fight ensued. After a few frustrating days the uproar moved to a part of Aboslute Write's forum which is not Google-cached (I doubt that the agent concerned realised how lucky he was with that); and it culminated in this particularly unprofessional tweet from him here.
This witty and concise livejournal post from Beth Bernobich provides a treasure-trove of linky background about the agent concerned: it's pretty safe to say that he has a history of being argumentative and confrontational online which doesn't bode well for how he might behave when negotiating a particularly difficult contract, or when dealing with editors who reject the books he represents; and I'm not convinced that a few years working in the book division of a product-licensing company is extensive enough experience, or is even appropriate, for anyone intending to embark on a career as a literary agent.
If you read through all the links supplied, you'll find plenty of reasons not to submit to the agent concerned: his lack of experience, his argumentative nature, and the extraordinarily bad advice he gave about children's books all count against him. But without all those things on a plate in front of them, how can writers avoid the agents who might not serve them best?
To paraphrase James McDonald, the job of a literary agent is not an entry-level position. If you're looking for a literary agent you'd be wise to avoid submitting to the new and unproved, no matter how well-behaved they are online. Wait a year and see how well they do: the bottom line is that a good literary agent will make sales to good publishers, at no up-front cost to the authors they represent.