The ad, of course, should say "fewer wrinkles." Mr. Rewrite will lean on his oh-so-expensive Chicago Manual of Style to explain.
Use less when referring to mass nouns or amounts. Examples: less water, less carbon dioxide, less hate.
Use fewer when referring to things you can count, also referred to as count nouns. It might be difficult to imagine, but if you had enough time you could count wrinkles on the exaggerated face at right. Other examples: fewer calories, fewer trucks, fewer accidents, fewer usage errors.
Garner's Modern American Usage notes this exception: Use fewer when count nouns really function as mass nouns. That means less is used correctly with time and money because you really aren't talking about specific minutes or dollar bills but the amount of either. Here are a couple examples of correct use:
- From AP: The U.S. Mint says the Oklahoma commemorative quarter will go into circulation in less than three weeks.
- From The New York Times: Mr. McCain would reduce the tax rate and also exempt all estates worth less than $10 million.
- With less students allowed on a bus, the district would look at purchasing additional vehicles to transport the same number of students. See more Google News examples.
- ... due to the Japanese car manufacturer selling 14,000 less cars than last year. See more Google News examples.