Cross-pollinating Campaigns

It works for botanists.  How can you make Cross-pollinating Campaigns work for you next marketing campaign?

The key element to understand about online marketing (and marketing in general) is that you will rarely (less than 5% of the time) sell someone on a product based on the first time they see your add.  It is a process.  For this reason, you need to be able to reach your targets on multiple occasions.  If you are able to do this, it is well proven that you will see a much better return on your investment while working with Cross-pollinating Campaigns.

The question is: can you see a similar “multiplier effect” when combining two separte campaigns?