Actually there are a variety of causes for blisters and in most cases leaving them alone greatly increases the likelihood of needing a more serious repair. The most common form of blistering occurs when water reaches the by products of the particular thermo-chemical reaction that occurs in some kinds polyester resins. This reaction produces acids that attack the bond between the fiberglass and the resin in the laminate. In doing so the blisters are able to expand deeper into the laminate by traveling down the surface of fiber bundles in the laminate. Over time this can greatly weaken a hull.
On the other hand, Tony, a dozen or so blisters is nothing to worry about, assuming that you seal them. You also do not say where the blisters are occuring. It is posible to have blisters between the gelcoat or barrier coat, and the laminate. In that case, the blisters are not structural but still should be addressed. I don''t know why you think this is hype but having been around cases where blisters were allowed to continue unchecked until the hull had pretty much delaminated through to the interior in large areas of the bottom, I assure you that it is not just an ''image thing''.
With regard to Jbanta''s comments, one minor point here, you do not want to use an epoxy paint to repair blisters as most epoxy paints are not really made to function as barrier. The best barrier coats are either epoxy resin or vinylester resins (there are advantages and disadvantages to both). In any case where the bliter extends into the laminate a repair with fiberglass and either epoxy or vinylester resin is warranted.