Berg Insight's new research report has totted up more than 7 million carrier-grade Wi-Fi access points worldwide at the end of 2012. It expects a CAGR of 13.5 per cent and an installed base of 15 million units by 2018.

In fact that seems a rather conservative figure when measured against the expected rise in installed WiFi-enabled handsets over the same period. These are expected to soar from 1.5 billion today to over 4 billion by 2018, a close-to three times increase while the base-stations expected to part-support them will only double.

Berg points out that unlicensed spectrum is an increasingly attractive solution for mobile operators as virtually all new smartphones now have Wi-Fi as standard and a majority of smartphone owners already use WiFi at home and at work.

But while most mobile operators have overcome their WiFi denial and now see it as a bit of a saviour, due to it relieving congestion on their mobile networks, exactly how all the new WiFi capacity is going to be used is still a subject of some controversy.

According to André Malm, Senior Analyst at Berg Insight, “the challenge for mobile operators is to integrate Wi-Fi with the mobile network in a way that enables control over the network selection and connection process.”

That's not a view shared by all observers who judge that many users will likely want to have - at the very least - 'seam-by-seam' notification of just what network their handset or tablet is trying to join... all the better to understand variable performance and to control costs.

Which, one might be entitled to conclude, is exactly why mobile operators are anxious to ensure that they can't... much better for the operator do all that and "control the user experience" on the user's behalf

A trenchant critic of this 'seamless' imperative is UK consultant Dean Bubley of Disruptive Analysis, (Operator WiFi: Seamless is the wrong approach) who points out that the telco view that seams are invariably bad things is not necessarily shared by users.

While a spot of WiFi seamlessness in the right place (when 'roaming' between home and office, say) might be counted a good thing there are many other cases where it's certainly not: "For example in the case of international roaming," writes Bubley in his blog.

"While it is undeniably convenient at one level for handsets to transparently connect to a visited network, the downside is that this can lead to "bill shock", anticompetitive pricing or conditions - especially for the dark art of data roaming. This is why the European Commission is currently trying to re-introduce seams, potentially allowing users to select a separate roaming provider to their home operator. It is also why so many users create their own seam - switching off data roaming entirely."

There may be at least 15 million 'seamless-capable' hotspots world-wide by 2018 but how much of the traffic flowing across them will be the result of seamless WiFi handoff is less certain.