How important are the plug-in retail-store-bought surge protectors for protection of household appliances? Is the danger primarily from lightning strikes and that sort of thing, or will normal fluctuations in the regional and local electrical grid produce surges? If it's a normal thing to expect from the grid, will the cheapest surge protector I can find be effective for that level of risk - do I just need the more expensive ones for protection from lightning and other unusual Acts of God? And if you've got a schpiel on surge protectors, sit down, pour yourself a martini and reel it off! (or link to it.) This question inspired by this web comic.