This means that you're getting A LOT MORE of the "window shoppers" and "information gatherers", as I like to call them, than previously.
"Window shoppers" are stopping by to check price at every place they can find before they purchase. They'll click every link available...then call a few places and try to haggle over price. With fewer competitors, you'll show up on their radar a lot more. The 'economy' tact works on this one as well -- many more people are price sensitive now.
"Information gatherers" just want to see what every site on the internet says about an item before they go to Wal-mart/Sam's Club/Big-Box-Store-in-your-Industry where the employees likely have little or no product training/knowledge. That way, they know what they want to buy and don't have to bother asking fruitless questions of your neighborhood's high schoolers. In my industry, where many of the item's require a tradesman's expertise to properly install, this is a significant amount of our traffic and callers and can greatly skew our conversion rate.
Unfortunately, these are both signs that your AdWords campaign is doing it's job...brining in visitors to your site on related key words.