Viral ads are getting harder to create

This BBC article about how ad agencies have had to change their campaigns over the last few years to encourage viral coverage is really interesting.

http://news.bbc.co.uk/1/hi/business/8280850.stm

From my online marketing point of view it is always hard to think up new ways of encouraging interaction with users, and I am only working on a very small scale. When you are trying to implement a national or even global campaign the push for innovation must be putting these agencies under great pressure.

As we are exposed to an ever increasing range of media our expectations grow, the ability to shock us gets harder and making something stick in our memory is near on impossible.

Cadbury's gorrilla and eyebrows campaigns have managed that, as have Compare the Market's meerkat. Any guesses which brand will manage it next?