You're not going crazy. Many people hear this noise; I believe I was one of the first, and MANY critics claimed I was insane or had other hearing problems.
First, I recommend you look at my site, dedicated to Logitech product flaws:
http://jdc.parodius.com/logitech/
FACT: This is an ENGINEERING FLAW in Logitech's wired mice. I have heard reports that some wireless mice do it as well, but I cannot confirm that, as I refuse to purchase wireless peripherals. This flaw goes all the way back to the MouseMan Dual Optical. It is not a new problem, therefore I must believe Logitech has known about it for many many years. You can read about the details of the problem on my site.
Logitech denies there's a problem of any sort. I believe the denial stems from a particular Support Manager at Logitech HQ in Fremont, California, who seems to have quite a lot of authority over not only Support but PR and some other areas of the company as well. The name of this particular manager I cannot mention here, as this individual has threatened legal action upon me if I mention their name, and/or their telephone number -- both of which I received from Logitech Support (WITHOUT asking for it!). This manager will do nothing other than plug your mice in, make sure the tracking and buttons work, and send your mice back with a note that "the mice work fine". You can see photos of the letter I received from this manager on my site.
This manager has, needless to say, made my quest to have this engineering flaw addressed quite difficult. I am no longer able to communicate with Logitech Support or Logitech in ANY WAY at this point; they tell me to "fax all questions/comments/discussions" to Logitech's legal department in Fremont, and can no longer assist me.
I urge other Logitech wired mouse users who can hear this problem (REGARDLESS of how far away your ear is) to contact Technical Support and bring this problem to their attention. Put pressure on them (but be kind and respectful of their Support representatives, as they're just doing their jobs; they're not to blame for this flaw) to have this problem addressed. This is something their Engineering and QA groups need to address.
Issues like these eventually turn into class-action lawsuits, where a company is forced to provide updated/revised products which fix the problem, or financial restitution, for those who bought the products. Constant white noise in your ear is *NOT* something that the FCC defines as permittable.
Rest assured, sooner or later Logitech will have to answer to the public for mice that are inducing ringing of the ears and other health-related problems (albeit minor, they're still health problems).
Additionally, I URGE Anandtech and/or other news/review sites to contact Logitech and interview them about this problem. If Logitech can admit there's a problem, it means we're one step closer to getting the problem solved (and I won't hold it against Logitech if they admit there's a problem -- admitting such establishes trust with their customers!). But sadly, I have done all I can at this point, as my hands are now tied due to legal threats and that sort-of thing. Public news sites are better suited to handle these kind-of communications anyways...
Please, Anandtech. Contact Logitech PR and see what you can find out. Do an article on this ordeal. Make it known to the public that these mice emit noise. Take a stand, if you can. Thanks.