I would not say that iMode required a lot of extra work to create content sites - on the contrary. cHTML was much easier to implement in the times and age of WAP 1.1 and 1.2 and even allowed you more flexibility in the graphic design. The DoCoMo guidelines (if you were an official CP) even helped creating a coherent design for different sites. The end user knew the workflow more or less.
I would disagree as well that iMode was a walled garden. Most content sites were off portal and everyone can/could create an iMode site.
iMode even had push email when no one else (not even Blackberry!) had it.
iMode’s problem reside(d) more in the fact that the handsets were from unknown/unattractive manufactorers. Not even Tier 2 manufactorer but 3 or even 4. When that latest rage was a new Nokia or a new Samsung on iMode it was the latest NEC or Mitsubishi. How cool is that ?
The other factor that did not help iMode is that for the old handsets content pages are limited to 10kB and for the newer generation its 20kB. Makes fast loading but impossible to add newer graphical features.
Data pricing was certainly an issue too, although it failed to take up in our home market, where the local cell-co (a KPN division) offered a sort of flat rate (7 euro for 20-30 MB which is a lot on iMode) for the access to it.
Lastly DoJa as opposed to MIDP applications were needed on most handsets - this did not facilitate the task of game developers outside Japan.
What iMode need(ed) as (more) handsets by Nokia, Samsung and SonyEricsson, MIDP applications and all the other stuff that works on ‘normal’ handsets.

iMode is for sure a walled garden.

The fact that iMode have set clear and strict limitations (such as 10k page size) mean that all sites not adhering to the iMode standard are out in the cold.

By setting such limitations iMode restrict the available content based on own assumptions of what users want, and the lacking success clearly shows that neither content providers or handset manufacturers, and more importantly the end users does not embrase such initiatives.

Alatto’s solution Tribes however is a true OFF-Portal solution that does not set any such limitations. The idea behind Tribes is to “Give People What They Want”.

Tribes as a proxy record all sites found by link clicking and rate these + all sites already in the TRIBES portal based on a number of factors.

The result is that Alatto provide the users with a dynamic personalised portal limited only by the users own behavior and preferences, and not by technical limits and assumptions from a portal owner.