There are two critical ingredients to engagement in mobile web services. First, a decent mobile web browser or native mobile applications (iPhone Apps being the best example, but there are others). Second is a data plan. Users willing to shell out $10 to $20 a month (adjusted for purchasing power) on a data plan. To illustrate this point more clearly and with numbers; EU (western) had 12 million more smartphones (phones with decent to great mobile web browsers). Yet, the US has considerably more (5M) users actually using mobile web services (email, browser, native apps). Well, in the U.S 32M users (14% of all subscribers) have a data plan versus only 10M (4.5% of all subscribers) in Europe (western) — a difference of 22 million users *. If you have a smartphone with no data plan you have a fashion accessory.
The chart breaks down average revenue per subscriber (monthly for the year 2008) between voice and data for some top countries. Note: Philippines & Indonesia users already spend 33% or more of their monthly bill on data services.