What Makes It Viral? explains "... merely suggesting email recipients forward your message to others is not viral marketing. Adding a line at the bottom of your email that reads "Feel free to forward this message to a friend" is not viral marketing ... Producing a message with a quality offer or an incentive for pass-along is what viral marketing is all about."
It may interest you to know there are viral marketing contests. People have to go from zero recognition and zero traffic to create a flood of traffic to win.
What makes it viral is a unique product with a strategic difference. Not a "tell a friend" script. Not a bunch of social chiclets.
The same digital economics which drive the cost of entry to zero on the web place a premium on originality. ...And not just the technical originality of having a different piece of stock photography, but a difference the customer values and the user can actually detect. Any site can be unique in the purely technical sense of not being a byte-for-byte copy. It takes some ingenuity to differentiate in a way customers find compelling.
What Makes It Viral is a Powerful Strategic Difference
Unfortunately that's something most offerings can't match. Gary Bencivenga merely repeats every copywriter from Gene Schwartz to Bernbach and Godin, "The better your product, the more persuasive your ad can be, and the bigger your marketing success. Clever copywriting technique is no substitute for a brilliant product. Consumers are too smart."
Lots of people want to "make it viral" the way they supersize an order at the drive through window. What makes a message worth passing along is a powerful strategic difference, which copy can then turn into a powerful offer.