The key is integration. Using one or two different mediums as communication just doesn't cut it. Marketers have to make sure that any interaction a customer wants is easily available to them. This means eliminating barriers to entry and offering calls to action.
This means, when signing up for say, an online newsletter, there should be at least another level offered. The article I'm referencing in Forbes specifies SMS advertising. Some interesting stats in the article regarding demographics of location based advertising specifics:
"64% of younger adults (18-29) prefer to receive the location-based offers but not far behind were 30-39 year olds (50%) and 40-54 year olds (42%)."
These stats are important to remember when looking at a key demographic for a product, or for a b2b operation.
http://www.forbes.com/sites/marketshare/2012/12/12/when-it-comes-to-mobile-marketing-integration-is-key/