There is a subtle difference between a shopping recommendation and a hardware recommendation:
A shopping recommendation can be a hardware recommendation, but is typically just somebody asking "what kind of widget should I buy to do foo?" or "which is better, the bar or the baz?". These types of questions are not helpful for a variety of reasons. For one, they become obsolete very quickly. For two, they're only really useful to that one person, because hardware is so specific to the individual's needs. Shopping recommendations like this are off topic.
A hardware recommendation can be a shopping recommendation, but can also ask about how to find hardware. This distinction is outlined in this Stack Exchange Blog post. It suggests that questions looking for hardware be presented in more of a "how can I figure out for myself which widget will fit my needs" manner. This type of answer takes more work, but instead of dumping a list of products which will soon be obsolete, provides much more valuable information about how to figure that out for yourself. These types of hardware discussions are permitted.
Now, let's take a look at the hardware-rec tag: of 202 questions...
- 140 are open and undeleted
- 62 are closed and undeleted
- 433 have been deleted
Obviously, we aren't allowing all hardware recommendations. Of the 160 open, undeleted questions, quite a few are very old, and were probably asked before we explicitly made shopping recommendations off-topic. A few are valid discussions in the how to choose rather than choose for me category, some also fall in the category of "hardware discussion" but aren't a shopping request, and a lot of them probably ought to be closed.
The hardware-rec tag is indeed a problem, since most questions tagged with it should not exist. I'm not going to take any action on it quite yet, since I'd like to hear feedback from the community and other moderators, but removing and banning the tag is one option. I will also be manually going through the questions in that tag and removing ones which are shopping recommendations. If anyone would like to boost their flag weight, feel free to go through them yourself and flag any that should be deleted.
Thanks for bringing up this issue. We'll keep this post updated on what the fates of the tag and its questions are.