[rimantas]

  > Mobile users won't necessarily need all the things Desktop users do,
  > since they usually have a very clear picture of what they want to do
  > on the site.

That's backwards. Desktop users want exactly the same that mobile users do. Desktop version has more only because someone thought "hey we have some space there why not to fill it with something?". That something is often most usless stuff.

  > PS: Please allow your users do "default" to a standard-version. I've seen
  > so many sites break on mobile phones, making them completely useless...

The thing is: the default version will soon be the mobile one. Take a look at Luke Wroblewski's "Mobile first" it's a good insight what's going on.

[algorithms]

The first point is actually the best thing that has come from Mobile Design thus far. It significantly reduced the amount of unnecessary distracting Ads on the page. Since, as you've said, they are usually used to fill the space larger Environments offer.

I've used the mobile first approach for my last project and I think a site isn't truly responsive if it hasn't a liquid(%) layout. Building those layouts is a pretty messy thing though :(

[gbog]

Hm, it depends. For a content or site, mobile first, which means a list of items without nothing on the sides, is probably the way to go, if you start from scratch.

But many other sites, apps, tools, can't be reduced that far. Take a calendar app, for example, it make sense to more on big screen in month view than on small screen.