Free mobile applications are great. If those free apps are supported by advertising, that’s a trade-off that I’m willing to make, and I suspect many users that would agree with me.

Our feelings about advertising in software have changed. While we don’t expect our desktop software to contain ads (sorry, no pop-ups when using Excel or Photoshop, please), everyone accepts that websites are supported by ads. That’s true of everything from blogs and reference sites to NYTimes.com and SDTimes.com.

Mobile apps—pioneered on Apple’s iPhone, but spreading like wildfire to other platforms, like Google’s Android and Microsoft’s Windows Phone 7—are more akin to websites than desktop software.

Consider: You might not install a Yelp or OpenTable application on your Linux, Mac or Windows notebook to help you find a restaurant or reserve a table. Instead, you expect to use its websites for that purpose: getting a free service in exchange for seeing some possibly relevant advertising. On your smartphone, instead of browsing to yelp.com or opentable.com, the natural tendency is to install a Yelp or OpenTable app, and both of those exist. If they showed ads, would you mind? Probably not.

This is a huge change of mindset. Ten years ago, in the very first issue of SD Times (Feb. 23, 2000), we published a story about an ad-supported software business model. We weren’t very happy about this. An editorial in that issue, entitled “It’s an Ad, Ad, Ad, Ad World,” said,

It’s bad enough seeing advertisements on Web pages. But ads in your applications software? The latest trend is to embed advertising links into client applications using tools from up-and-coming companies like Aureate Media Corp. or Conducent Technologies Inc.

On one hand, that’s good news: Vendors are developing alternative revenue streams, which might allow them to offer full-featured applications for free or for reduced cost.

But the bad news is: Your employees are trying to do a job. To protect them, your company doubtlessly stops salespeople at the door and won’t allow them to canvass your busy employees while they’re working. Should embedded advertisers be afforded special privileges and 24×7 access to your staff? Of course not.

If you’re developing consumer applications, embedded advertising for your freely distributed software is a good idea, and can provide a valuable source of additional revenue for hot products. But please don’t inflict ads on your enterprise customers because, frankly, they won’t stand for it. Would you?

Yes, the world has changed. Ads embedded into mobile apps aren’t only tolerated, but are embraced as a legitimate business model. In fact, Google is buying AdMob, a company that helps developers embed and sell ads in their mobile apps, and Apple has announced its own ad delivery system, called iAd.

Just don’t make the mistake of charging for an app… and then embedding ads anyway. Cable News Network has committed this faux pas with its US$1.99 CNN Mobile app, and the feedback is scathing. Here are the titles of the three more recent customer comments:

DO NOT BUY THIS APP! It’s full of advertisements!
Ads (!) – In a paid app – a ripoff!
Slow, littered with ads!

From websites to mobile apps, it’s an ad, ad, ad, ad world. But I guess we’re used to it.

Alan Zeichick is editorial director of SD Times. Follow him on Twitter at twitter.com/zeichick. Read his blog at ztrek.blogspot.com.