Gabby
Thanks for posting such a thoughtful comment.
I can only see two benefits of "assumption personas" like this. The first is that the design team has preconceptions, so at least assumption personas get these out in the open where they can be questioned. The second is that assumption personas highlight conflicting beliefs on the design team. In either case, you need field research to resolve the issues, so I'm not convinced the assumption persona has got you anywhere. More seriously, with an assumption persona you risk ending up with a stereotype, rather than an archetype, making the team even more blinkered in its thinking. Another problem is that the design team loses the enthusiasm to develop personas as they already have one — especially, as you point out, because real personas take time and money to develop.
The aim of the article is to provide guidelines to make personas believable, hence the article headline. I agree with your comment that developing personas is only half the battle — publicising them is equally critical. I've written about selling usability to your manager elsewhere.
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Your article, while clearly well-intentioned, misses the mark in some key areas.
Though it's usually always best to have personas that are driven by qualitative and quantitative research, it's not always necessary, in terms of project size, time and budget. There exist projects for which it is perfectly okay to fake your personas based on a random sampling of friends, family and non-involved coworkers. Any data is better than no data. It also serves to help get your mind inside the user's needs and wants.
I'd also add that the article headline is more than a little misleading: getting the entire design (and project team, not to mention the client!) to embrace and use your personas often takes far more work than simply following the guidelines presented. One can hardly walk up to a Senior Art Director and say, "Look here, Brad, these personas are based on tons of ethnographic research--so you best use them and love them!" At that point, of course, Brad will take an Xacto knife to you providing he doesn't double over in laughter.
The use and regular adoption of personas as a design, strategic and innovation tool require one's own empathy and patience as you educate and partner with your team and client.