OK, so I'm having a cranky day, so I'm going to go off on a tangent. A few weeks ago, I was reading an article on Agent Query, and it was giving authors advice on not requerying or sending another email to ask if the agent received the first one. Basically, it was saying that agents are doing authors a favor by letting them send email queries and that these queries are a step above spam. If an agent decides not to respond to these emails, then the author just needs to accept that and move on. I have a couple of issues with this approach: 1) as the world continues to go paperless and technology becomes more convenient, it is not going to be a favor for agents to do this, it's going to become the norm and 2) it may only take a second to delete the email (which most do if they are not interested), but it would only take two more to hit Reply and say "No, thank you" (or if they're real short on time, just "No"). Not only would it give authors piece of mind, but it would cut down on those unwanted extra emails asking if they received it.
I know agents are busy, and I know they need to focus on their clients, but authors need to know that their work hasn't been lost to the void. If nothing else, have the assistant who is stuffing rejections into envelopes take some time out of their day to type a quick "No." It can be that easy.