If you plug in your iPad/iPhone/iPod then iPhoto or some proprietary image transfer application automatically opens even if you don't want it to, because the device is regarded as a camera.
You can change this behavior by using Apple's Image Capture utility to set defaults for each device.
This problem has been plaguing me for a while. I have a Nikon DSLR, a Canon Point and Shoot, an iPad, an iPod touch, and now an iPhone. All of them are treated as cameras when I connect them via USB.
I frequently use Nikon Transfer to move images from the Nikon DSLR, and it always opened no matter which of these devices I connected. The preferences in Nikon Transfer don't help, and the options in each of my iDevices preferences gave me nothing to manage this either.
So, when I was digging through Image Capture (it's in /Applications) to decide how to handle my new iPhone's images, I found a device list on the left, and options to change what app would open when you attached them. Once can even determine where to move/copy files on the hard drive. I set my iDevices to open no app when connected and now the only thing that opens Nikon Transfer is my DSLR.
[crarko adds: Image Capture is one of those very useful and often overlooked utilities. It's worth getting to know better.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20111106175631541