I think it would depend on what you're selling. The more specific your tag is, the more likely it will be searched by someone looking for that item. In other words, if you put 'recycled' as your tag, and someone does a search for a '1965 recycled Brunswick Pool Table', your item will eventually come up, along with the thousands of other recycled items. But if you were to ad 'recycled pool table' it would be hit much less, but the odds of making a sale would be greater. So I think its better to be more specific and be searched less, because it's more likely to generate a sale....