SAN FRANCISCO -- Salesforce.com (CRM) - Get Report first's acquisition may be a sign that the upstart software company is growing up.

Salesforce said Tuesday that it will spend $15 million to buy privately held

Sendia

, a small software company whose technology enables Web-based applications to be accessed via a variety of mobile devices.

Sendia has been a partner company for some time, but its small, engineering-oriented staff has not had the marketing muscle or acumen to have a major impact, says David Dobrin of B2B Analysts, a Cambridge, Mass., research firm specializing in business software.

"It isn't yet clear if its success was limited because it is too small, or because Salesforce is wrong and its customers don't really want mobile applications," he said during an interview at San Francisco's tony Four Seasons Hotel, where the acquisition was announced Tuesday afternoon.

If the demand is indeed there, Salesforce's large and aggressive sales and marketing organization could tap into a significant new revenue stream as increasingly mobile workers clamor to increase their efficiency on the road. "Workers don't want to be tethered. The lack of mobility has been a major drawback for Salesforce," he said.

In two years of operations as a venture-funded company, Sendia has attracted some 2,700 subscribers working at 79 different companies, says CEO Alex Klyce, who will become a senior vice president at Salesforce. As of late January, Salesforce had approximately 20,500 customers and about 400,000 paying subscribers.

Salesforce CEO Marc Benioff says that a third of his customers want to access applications on the road as well as in the office -- and it shouldn't matter what type of device they want to use.

Salesforce has added a layer of software to its infrastructure that can be programmed to work with numerous handheld operating systems and devices. But developers writing applications for Salesforce customers won't have to worry about which handheld device will run the application. "Mobility will be the default," says Benioff.

Although Klyce wouldn't divulge his company's revenue, a back-of-the-envelope estimate indicates that because Sendia was charging $50 a month to each of its 2,700 subscribers, it was likely on a run-rate of about $1.6 million a year.

Salesforce expects the acquisition to reduce earnings by a penny a share in the first fiscal quarter and by 3 cents to 4 cents a share for the fiscal year.

Benioff, meanwhile, has reduced his stake in the company he founded by 5.4% this year, while selling 1.3 million shares for just under $50 million, according to data collected by InsiderInsights.com. He still owns 22.8 million shares.

In an interview, Benioff said the selling is "a routine, transparent diversification," made under the

Securities and Exchange Commission's

10B5-1 rule, which allows insiders to sell stock automatically.

Jonathan Moreland, research director for InsiderInsights and a contributor to

RealMoney.com

, gave Benioff's trades a clean bill of health, saying they have none of the characteristics of a founder seeking to cash out at the possible expense of his shareholders. "There's nothing there that throws up a red flag," he said.

Automatic trading under 10B5-1, said Moreland, can be subject to abuse, because the rules governing the trades easily can be changed by the shareholder to reflect expected events in the market.

"My trades are consistent. I sell a very small percentage every day and have not modified the rules," says Benioff.

Insiders as a whole have sold Salesforce shares worth $72.4 million this year. The company's stock, down close to 2% in recent trading to $32.71, has fallen on hard times in the past month; it traded near $40 in mid-March.