One of the downsides of doing something of the sort is that all comments will not be sunshine and roses, and given that the stated purpose is to name products and comment on them, some negative comments may come across to the manufacturer in question as libelous. It's a long shot, I know, but we don't allow such comments because of the litigious nature of today's society. There is no guarantee that because a negative statement is true, the party of whom it is said will simply allow it to pass without comment. And there are companies out there who actually search the Internet for just such comments, with the intent to sue them out of existence. And remember, also, that one does not have to be guilty of anything in order for the defence against such a suit to be financially ruinous. Is company X going to come after you? Of course not. You have the anonymity of the Web to protect you. Anne and TCS do not. So you know who's going to get caught in that meat grinder.
Sorry for the doom and gloom. There's nothing stopping you from asking for comment on a product, but know that if there's anything said that's questionable in this regard it will likely get pulled. So perhaps it's best to confine the less than complimentary comments to PMs.