Mobile advertising set to double.

And users don’t mind… in some cases.

In a new report, “US Mobile Marketing forecast: 2006–2011,” JupiterResearch predicts that advertising for messaging and display ads for mobile devices will more than double over the over the next five years.

Jupiter projects that ad spending will rise from $1.4 billion this year to $2.9 billion in 2011.

The rise will not come without some fundamental changes, however.

“Educating consumers, protecting their privacy and mitigating their concerns about the cost of commercial text messages and SPAM, will be key to driving consumer interest and adoption of mobile marketing executed with SMS,” said Julie Ask of Jupiter.

In related research, concerning consumer attitudes to mobile advertising, Harris Interactive found that 26% of current mobile phone subscribers would be willing to watch advertising on their mobile phone — if in return they received free applications.

A much smaller number, only 7% of wireless subscribers, said they would be interested in receiving promotional text messages “if they were relevant.”

“This seven percent ‘coalition of the willing’ represents a huge market given the fact that there are over 200 million cell phones in the United States,” said Joe Porus of Harris.

But he too had a warning for wireless service providers: “[They] need to balance the value of advertising revenue with the potential of irritating their subscriber base which could potentially increase churn.”

Obviously, the growth of mobile phone advertising is coming, but not without some trials and tribulations first.