In my opinion, to say skiing backwards = switch is wrong.  It always has been and always will be.  This issue has been debated for many years, beginning on the old FREEZE and PBP forums.  No one ever agreed on what to call backwards skiing.  Likely, no one ever will.  Either way, it's skiing's loss.
The only reason people call backwards skiing "switch" is because a handful or pros, back in about 1998, arbitrarily gave it that label.  For those of you who remember the Summer X-Games big air in San Fran will recall Vinnie's fakie 3.  Unfortunately, people like Mike Douglas started calling it a "switch 3".  The use of "switch", especially from such a person as the Godfather of freeride, eventually stuck.  As much as Mr. Douglas is one of the most brilliant skiers ever, he got this term wrong.
It comes down to the simple fact that what switch means in all other sports is "unnatural".  If you do something switch then that means you're doing that trick unnatural.  It could be a spin or a grab or whatever -- it's just done unnaturally.  For some people, spinning left is natural.  For others spinning right (darkside) is natural.  Depends on the person.  Fakie, on the other hand, means "backwards".  You ride fakie, then you're riding backwards.  They're two separate terms with two separate meanings.  It's mind-boggling that skiers have insisted on mixing up their definitions and then duplicating their applications.
Bluntly, by definition, skiing backwards cannot be skiing switch.  This is because no one skis backwards as their "natural".  EVERYONE skis forward naturally, so the term "switch" does not even apply to forwards or backwards skiing.  Its use as backwards skiing is simply wrong.
Here's a mind-bender: Some of you may also remember the same San Fran X-Games where the snowboard announcer called Shane McConkey's fakie back a switch front.  Was the announcer correct?  You be the judge.
If skiing is to be respected by other sports such as snowboarding, skateboarding, in-line, surfing, etc., then we should adopt the same vocabulary that's been working fine for years, and reject misguided trends.
Calling backwards skiing switch because it sounds "cool" or has less syllables are empty arguments and lazy.  Hopefully the next generation of skiers will straighten this issue out and put it to bed.