Editor's note: Amy Gahran writes about mobile tech for CNN.com. She is a San Francisco Bay Area writer and media consultant whose blog, Contentious.com, explores how people communicate in the online age.
(CNN) -- Despite online security concerns, the number of Americans who use mobile devices to access financial services is growing fast, according to new data from comScore.
In the fourth quarter of 2010, almost 30 million Americans accessed their bank, credit card or brokerage accounts from a cell phone or tablet, up 54% from the same quarter a year earlier.
Here's how that growth breaks down for the three primary mobile banking channels (note that some people use more than one):
Smartphone/tablet app: 10.8 million users, 120% increase
Mobile web browser: 18.6 million users, 58% increase
SMS text messaging: 8.1 million users, 35% increase
Nearly half of those surveyed say they primarily access financial services online via a desktop or laptop computer; but 26% said they primarily use mobile services for banking. Only 10% of respondents primarily do their banking in person at a branch, and only 4% primarily handle their banking via voice calls.
New services that help people avoid trips to the bank or ATM may be helping boost the popularity of mobile financial apps. For instance, many major banks now offer smartphone apps that allow you to make a deposit by taking a picture of the front and back of the check.
Why don't more people access mobile financial services? comScore found some interesting differences between smartphone users and the nearly three-fourths of U.S. mobile users who own feature phones (simpler phones that are the next step down from smartphones).
The biggest obstacle to using mobile financial services is simple habit or preference: 53% of smartphone owners and 45% of feature phone owners reported, "I prefer to conduct my transactions online from a fixed device."
Intriguingly, a quarter of smartphone users reported, "Accessing my account through my cell phone is too slow." Yet only 9% of feature phone users had the same complaint, even though feature phones typically rely on slower wireless data networks and have browsers that are more limited and harder to navigate.
Roughly a third of both groups reported concerns about mobile security -- and there is reason for concern. In October, Banking Info Security reported that even though computer-based internet access to banking probably poses more security risks, most banks now have a decade or more of experience with managing those risks.
In contrast, most banks have less experience with mobile services and their attendant risks, and so the risks are amplified by what the banks simply haven't learned yet.
Last fall, the Wall Street Journal reported that several banks were rushing to fix security holes in their mobile apps, mostly regarding how the apps were storing data on cell phones.
In general, if you are using a mobile financial services app, it's a good idea not to save your password in the app. Also, it's more secure to use the app over your wireless carrier's network, rather than on an open Wi-Fi network. And, of course, remember to lock your phone with a security code or pattern.
The opinions expressed in this post are solely those of Amy Gahran.