Growing up in the business, the tagline was always the apotheosis of the craft of advertising. The tagline represented what a company stood for, what made it unique usually in eight words or less.
"When it absolutely, positively has to be there overnight."
"The world's most experienced airline."
"The ultimate driving machine."
"We run the tightest ship in the shipping business."
"It takes a tough man to make a tender chicken."
Today, lines like the above are excoriated as old-fashioned. They don't evoke images of happy people gayly using your product. Instead they involve your brain and thinking.
Flip's tagline "Do you flip?" was existential in its meaninglessness. It did nothing to say what Flip did well or better than anyone else. It merely asserted that you were happy if you flipped.
A case in point, and one I've written about before, is BMW. They now use the single word "Joy" as their tagline. (Hopefully, now that they've fired their agency, they'll retire this line.) Joy is not ownable, not unique, not intrinsic to the brand.
Taglines have gone from brand to bland.
If you can put it on someone else's ad, it's no good on yours.