According to Ziff Davis Media's annual "Digital Gaming in America" survey of more than 1,500 randomly selected U.S. households, cell phone gaming continued its meteoric rise in 2005: the number of households engaged in cell phone gaming nearly doubled again, jumping from 16.3 million last year to 27.9 million this year.

The 2005 Digital Gaming in America study reveals a number of surprising shifts in mobile and portable gaming habits and consumer preferences. Mobile phone gamers in the study reported spending 19 minutes per gaming session. They spent an average of $13 on mobile phone games in the last 60 days, and core gamers spent even more on mobile phone games - $19 in the last 60 days.

("Core gamers" are defined as those who bought four or more games in the last six months and play ten or more hours per week.)

Respondents who do not play games on their phones cited small screen sizes as the primary deterrent (cited by 49% of respondents); they also cited a lack of desirable games (46%) and high costs (35%) as reasons they don't yet play cell phone games.