News that Telstra plans to build a national wi-fi network, as reported by The Australian and Fairfax mastheads, shouldn’t come as a shock. Given the volatility of anything and everything to do with mobile internet use, nothing should surprise us any more. But it should scare you.

Telstra’s plan, which is being announced right on Crikey‘s deadline, will — according to tweets from ZDNet‘s Josh Taylor — reportedly see $100 million spent showering the country with new modems for broadband customers who choose to act as wi-fi hotspots using Fon sharing technology. It’ll be free to use by the telco’s fixed broadband customers, although any data used will count towards their quota, and a “small daily fee” for others.

Arranging free wi-fi for fixed broadband customers is not uncommon in Asian and North American cities, although the Fon sharing is a less common twist, and it’s a logical move for Telstra for the same reasons. It makes the telco’s fixed broadband packages more attractive, it reduces the load on 3G/4G mobile broadband services in high-traffic areas, and — not talked about so much — it provides more opportunities to track customer behaviour for all those data mining and monetisation strategies that make modern telcos into something much more like a media company.

For all the hype around the “mobility revolution”, and while consumers are increasingly using their mobile devices away from the home or office, the growth in Australia’s mobile broadband market was just 3% in the 12 months to December 2013, according to research released yesterday by analyst firm Telsyte.

The proliferation of public wi-fi hotspots, which Telsyte analyst Alvin Lee says are “sprouting like mushrooms and are now widely supported by local councils, shopping centres, local businesses and increasingly our transport networks”, means that there’s less need for a dedicated mobile broadband device — particularly as most smartphones can now operate as a wi-fi hotspot, and people are becoming more comfortable pressing that button.

“The opportunity for dedicated mobile broadband is diminishing even as mobile traffic continues to grow,” Lee said. As a result, Telsyte believes telcos will only be able to monetise 20% of the consumer media tablet market.

Indeed, why would anyone want to load yet another device into their pocket, perhaps with yet another charger, and certainly with another monthly bill?

Whether this will play out well commercially for Telstra remains to be seen. As Fairfax’s David Ramli points out:

“Other Australian companies have attempted to use Wi-Fi hotspots to give customers more internet services on the go with very low success rates.”

iiNet sees its wi-fi offering more as a marketing tool.

My weekend in San Francisco showed how this might play out. AT&T has wi-fi hotspots across the city, and you see their branding every time you look for a connection. It left an impression. But at the same time, most bars, cafes and shopping malls have “free” wi-fi too — along with power outlets and somewhere to sit.

“Free” is in scare quotes there because the use of wi-fi for tracking consumers is becoming ever more sophisticated. Toronto-based Turnstyle is just one of the companies pushing the boundaries in this regard. By rolling out a unified wi-fi network throughout the shopping district, they can track people as they go about their business. As The Wall Street Journal reported in January:

“Turnstyle’s weekly reports to clients use aggregate numbers and don’t include people’s names. But the company does collect the names, ages, genders, and social media profiles of some people who log in with Facebook to a free wi-fi service that Turnstyle runs at local restaurants and coffee shops… It uses that information, along with the wider foot traffic data, to come up dozens lifestyle categories, including yoga-goers, people who like theater, and hipsters.”

If Telstra is planning something similar — and given that this is increasingly the way things are done, I suspect it’s likely — then this could be the start of one of the most comprehensive consumer tracking databases in the country.