It is said that a school of piranha can skeletonize a cow in minutes. This bit of trivia is apparently based on something of a deception-- some South American officials had intentionally starved a school of piranha so they would be in an eating frenzy when they threw the cow in, all as a ploy to impress Teddy Roosevelt-- but it is technically true.
Authors querying agents are trying to impress said agents, but given the market out there, they start to feel like those starved piranha. And I can see how for the agents, they can feel a lot less like Teddy Roosevelt, and more like the cow.
While we, the querying authors, don't really see the level of electronic assault I'm sure most authors get, one easy way to get a sense of it is to look at Nathan Bransford's blog today. To celebrate his 1000th post, he offered a query + 5 page critique to the 1000th comment on the post. Nathan is probably one of the bigger agents out there in the agenting-blogosphere, so this offer was widely read and amongst the querying, a highly coveted prize.
How coveted? Said 1000 posts took less than two hours. The last 250 posts of that thousand? Six minutes. And that's probably not even counting the attempts (like myself-- I'm not claiming I'm any different) that tried to post in that window and got hit with some sort of server-crashing error.
What's my point? I'm not completely sure, other than while it really sucks to be one of a swarm of hungry fish... it's important to remember that it's pretty tough on the cow, too.