I know what you're saying, but to do this properly would need more than volunteer effort. There would be so many reviews, and comments on reviews, and discussions, and whatnot, that it would be impossible to find what you're looking for without some fairly heavy-duty IT skills behind the scenes.
MobileRead already has a review section,
in the Wiki, where I see carandol has already given the treatment to one of mine. No reason why we shouldn't start adding our own reviews and comments, and maybe in time the data there can be presented in a more conveniently searchable way.
An appeal to everybody: if you have posted reviews anywhere else, and you still own the copyright (as I'm pretty sure you will, though check the terms & conditions on the site where they're at), and if you have a spare moment, why not cross-post them here?