According to a new report, some 50 million workers in the U.S. have jobs that allow for at least part-time telework, but only 2.9 million are actually doing it.

But considering the lack of clarity in definitions of telework, determining the accuracy of that number, and other telework data, is tricky, as Gary Audin writes over at NoJitter. The report he references is the result of some numbers-crunching from a mix of mostly-governmental data sources. Our guess is that it gives a more-or-less accurate overall view, but we wouldn’t stake a business decision on any specific data point.

For example, are teleworkers and mobile workers different, and how much so? Both work outside the traditional office for at least a significant majority of their work hours, but we think of them differently. While both of them might – rather, should – take advantage of collaborative Unified Communications tools, there will be quite a difference in the way each uses them.

There are some interesting bits of data, in any case. For example, the number of people teleworking grew by 61 percent from 2005 to 2009, and while private sector telework accounts for 76 percent of the total, the number of public sector workers is increasing both absolutely and as a share of the total. The bigger the company, the more likely teleworking is allowed or encouraged, and a guesstimate puts the fuel savings for all of today’s teleworkers at about 390 million gallons of gasoline annually.

A couple of obstacles to telework do seem to persist. One is the attitude of the insecure manager, who figures if he or she can’t see the teleworker, is that person really working? We’ve always felt that if a manager can’t tell without visual confirmation whether their salesperson is making sales, their writer is producing, or the customer service calls are being answered, there is a problem – and it’s in the manager’s abilities. Especially now with collaboration tools such as presence, that make it possible to know a person’s location and status.

The other obstacle is that for some people, the all-telework environment is challenging because of the lack of in-person social contact. Sometimes that can be remedied with once-a-week meetings at the office, but there are personality types who just don’t do well in relative isolation.

Audin predicts, no doubt correctly, that the percentage of people teleworking and the interest in it will increase as the next generation enters the workforce. After all, as you can see in just about any public place, these teens and college-agers are very screen-oriented, often to the exclusion of people around them. So the social contact aspects of the job likely won’t be as big an issue for them.

Funny, it used to be the common observation about techies that they rarely made eye contact. (Old joke: How can you tell if a techie is an extrovert? He looks at YOUR shoes while he’s talking to you, rather than his!) Now we may have a whole generation like that.