Current practice is to plug a microphone into a microphone preamplifier, then into an audio interface that connects with the computer running the recording software of your choice. Often the audio interface itself has a mic preamp built in.
When you think about it, wouldn't it be a good idea to short-circuit this chain and equip the microphone itself with a USB socket so it can connect directly to the computer? The mic pictured is a Blue Microphones Snowball, and it is indeed USB-equipped.
This is an interesting concept. It's new and definitely worth trying. Whether it is actually better will remain to be seen. Perhaps it will have certain applications in which it excels; others where traditional solutions are more appropriate.
Obviously there is a simplicity and elegance in dispensing with the preamplifier and interface. But what have you lost? The gain control for one thing, unless the microphone has one (of course it will have to have an internal preamplifier). Perhaps you will need to take a walk to the mic to adjust the gain. That will be irritating.
Perhaps the gain will be controllable by software. But that has brought complication back in, and anyway this is something that can only be achieved optimally with physical electronic components. Perhaps a USB mic should incorporate a motorized potentiometer to act as a remotely operated gain control.
The next question will be how do you use several USB microphones simultaneously, which with normal mics is a capability you take for granted? Can you connect them via a USB hub, or will this slow things down too much?
Ah yes, cable length. A conventional microphone can drive a cable 100 meters long without too much signal degradation. Even longer distances are perfectly practical. But a USB cable – five meters really is the limit, unless you use repeaters. However, five meters is perfectly adequate for most home recording studios.
It isn't time for a conclusion yet. USB microphone are an interesting phenomenon that might have unexpected benefits. Perhaps we will see 'upmarket' FireWire microphones next.
It'll be fun!