I use tags for browsing categories, and I use searches for finding something specific.
When you go in to a library wanting a sci-fi book, you go to the sci-fi section, or even look for an aliens area (tags). And when you are looking for something specific, such as Terminator, you will search for it... or search more specifically (searches).
That's how I use and think of tags, whether its right or wrong I don't care. It works well for me that way.
May be a bad example I don't know, hopefully my point came across correctly.