A year or two ago we put up some websites which were specific to brands we own. Sure enough those sites (eg 'myBrand.com') started to rank pretty well for those brand terms eg 'mybrand curling tongs' (it's not curling tongs, btw, but you get the idea). We were getting a decent amount of traffic presumably from people who have bought or seen these products on our amazon/ebay stores.
Before long, we see us starting to rank well for non branded searches eg 'curling tongs' even among decent competition. Next thing you know I'm getting told by the boss that we need to put up websites for all specific ranges, not just brands, because specificity is a bonus for ranking well.
While there's probably a point that a site for MybrandCurlingTongs lends itself well to ranking for curling tongs, is there also an element that the branded searches we got (via making our brand known on amazon/ebay) helped the site gain recognition and authority? As such a new website about 'ionising hair dryers' would not rank well based on being specific, because it wouldn't be helped by a lot of branded traffic?