Data usage by US smartphone users has risen by 89% Y-o-Y

"The mobile Data Tsunami initially described here is still growing at an astounding pace. According to Nielsen’s monthly analysis of cellphone bills for 65,000+ lines, smartphone owners – especially those with iPhones and Android devices — are consuming more data than ever before on a per-user basis.  This has huge implications for carriers since the proportion of smartphone owners is also increasing dramatically.  (Currently, 37% of all mobile subscribers in the United States have smartphones.)
In just the last 12 months, the amount of data the average smartphone user consumes per month has grown by 89 percent from 230 Megabytes (MB) in Q1 2010 to 435 MB in Q1 2011. A look at the distribution of data consumption is even more shocking: data usage for the top 10 percent of smartphone users (90th percentile) is up 109 percent while the top 1 percent (99th percentile) has grown their usage by an astonishing 155 percent from 1.8GB in Q1 2010 to over 4.6GB in Q1 2011."

Source:  Nielsen Wire, 17th June 2011