The strongest confirmation of the situation is also the simplest: Canonical has yet to announce profitability.
In fact, although many of the desktop services are recent, it has yet to make any public statement about their successes.
For that matter, so do its affiliate partners. Amazon.com, for instance, did not even bother to mention the partnership with Ubuntu in its news releases. Amazon's news releases have been known to mention individual book titles, but they don't mention Ubuntu. That suggests that Amazon has yet to derive any significant income from its association with Ubuntu and has little immediate expectation of doing so.
In the same way, a resounding success for a desktop service would be a first. It would open up the idea of an operating system as a new distribution channel for entertainment services. Just as importantly, even if Canonical remained unprofitable, such a success would improve its image. Not talking about it would be tactically unsound.
Canonical may still struggle to profitability. For the last few years, it seems to have been opting for a shotgun approach to its business model, trying a variety of approaches, options and features without relying too much on any one option.
Yet although Canonical has taken commercialization of the Linux desktop further than any other company, it appears to have been no more successful than its predecessors.
In fact, when Canonical's founder, Mark Shuttleworth, stepped down as CEO to focus on his interest in usability, he may have repeated the mistake of previous distributions and allowed Canonical to be distracted by the desktop. Instead of developing Unity, perhaps Canonical would be closer to profitability if it had spent the last three years developing a line of commercial services rather than focusing on branding and usability.
The Linux desktop has been a dead end for countless companies in the past. Ubuntu has probably been more successful than any other company that has invested heavily in the desktop, but so far, there is no reason to think it is an exception. Eventually, that might change, but even that seems debatable.