> In a nutshell, they say that Rails starts to get less appropriate for apps
> with transactions that encompass entities other than just the database. If
> the server side objects also modify the data, and particularly of the
> modified objects then affect other objects, then it can become very non-
> trivial to handle all of that in Rails.

Since each request is handled in isolation, you rarely encounter
situations where object changes ripple through with tons of
consequences. At the end of each request, you'll have to persist your
data somehow, so whether that's in a database, Madeleine store, or web
service call, I don't see that being all that different.

Perhaps these guys are just solving different problems. But I found
the rant to be very abstract and hard to relate to. If you can come up
with a concrete example, I'd love to give a more concrete answer to
these concerns.
-- 
David Heinemeier Hansson
http://www.loudthinking.com -- Broadcasting Brain
http://www.basecamphq.com   -- Online project management
http://www.backpackit.com   -- Personal information manager
http://www.rubyonrails.com  -- Web-application framework