It's a question I've heard that sometimes comes up with dualists, and they tend to act as if it's a problem for materialism and neuroscience. I think I caught Nick asking something like this before I shifted the debate. (Feel free to pick it up over here.) Quite frankly, I see it as one of a myriad questions dualists have to answer. Neon Genesis Evangelion answered it with the completely fictional "AT Field" that kept people from turning into orange Tang until that trippy movie. But mostly bent space into a nearly indestructible forcefield in the series. Or something. NGE's weird.
The reason I can't read your thoughts is pretty much the same reason why my laptop doesn't pick up Armored Core data from my CD/DVD/Blu Ray shelves, memory cards, or my PS3's harddrive. They aren't connected. There's no Playstation memory card slot on my computer. The disks are on the shelves, not in my drive. My PS3 and laptop aren't configured to talk to one another.
And until we get up to Ghost in the Shell, with our brains in robot bodies (with chainsaws for hands! Bzzzzz!), my brain doesn't have any hardware to connect with yours. For now, we have to settle for very indirect communications, like text and speech. And there's a lot of interpretation layers to get past. I process information differently than you. I reject anecdotes as "silver bullets" in an argument, for example. I do this because I know there are more reliable forms of evidence that produce more consistent results.
But back to the point: This bizarre argument is a problem for dualism, not materialism. Dualists are still in dire need of a description of the soul, and they need it to explain why there's no data leaking between souls. My computer isn't playing Samurai Champloo right now because the DVD's too far away and not aligned with the laser in my laptop's drive. I'm not reading your thoughts because there are no neurotransmitters or whatever relaying information between our brains. Undetectable, undefined souls, well, you dualists out there still need to explain.