They do have one major flaw, however: they're highly susceptible to water. Commercial waterproof matches are available, but they're expensive, and far harder to come by. Fortunately, there are several ways to waterproof your matches:
Waterproof cases are the most basic starting point of protecting your matches. A waterproof case will keep your matches together and protected from water and damage, and most of them have a rough surface for striking your match.
If you're equipped to safely melt paraffin wax, it makes a dandy waterproof coating on any number of things, including matches. Simply melt the wax and dip your match heads into it, then let the wax cool and harden. When you're ready to use them, simply scrape the wax off with your fingernail, and strike as normal.
Melting wax has its hazards, though; and is not something to be undertaken lightly: hot wax can burn skin, and can also cause a very serious fire. Don't try it if you're unprepared and don't have the proper gear.
Turpentine is a wonderful, very safe method of waterproofing matches, but it must be renewed about once a year. Simply pour an inch or so of turpentine into the bottom of a small glass (one you don't care for, since you won't want to drink from it after), and stand several matches head-down in the turpentine for five minutes. Then, lay them out on a paper towel or piece of newspaper to dry for about half an hour. Your matches are then ready to go; just strike them as you otherwise would.
Probably my favorite method of waterproofing matches (and sealing various other things) is clear nail polish. It doesn't necessarily have to be clear, but Grandma used clear nail polish for all manner of things, and who am I to argue with Grandma?
Simply open your bottle of nail polish, and dip your match heads into the nail polish. Wipe any excess against the bottle rim, and let your matches dry, with the head not touching anything. As with turpentine, they'll strike as-is. However, nail polish dries hard and durable, and will provide a little extra protection for your matches.
Sealed Pouches: This page has a wonderful guide to sealing your matches in simple waterproof packets. Other things like tinder can also be sealed in this manner, and be safe and ready when you need to crack them open and use them.
Keep 'em dry!