> A NSL isn't diametrically different than a warrant.

The whole judicial oversight is the main and most important difference. Justice is supposed to be a balance and in these case the other side is loading the scale.

A NSL is a government order to produce something, so is a warrant. The difference is that a warrant has oversight as a check against abuse, and a NSL has removed all oversight (no judge, can't talk about it, etc).

  | The whole judicial oversight is the main and
  | most important difference

Not necessarily. If Google (or whomever) could publish all of the NSLs that they get, it would have the possibility to cause public backlash that spurns Congress into action. Let's not forget that if we use the 'secret court' (e.g. FISA) to approve these NSLs, there's a 99.9% chance of them being approved. The FISA court rarely rejects what is put to it (which makes it sort of telling that the government doesn't even want to deal with the formality of the FISA court).

  | Justice is supposed to be a balance and in
  | these case the other side is loading the scale.

You are trying to say that because you don't like National Security Letters, but you do agree with warrants that they have to contain no similarities. I disagree with NSLs, but talking about NSLs like warrants without judicial oversight doesn't require some addendum of, "OMG! NSLs ARE NOT WARRANTS! WAKE UP SHEEPLE!"

Well, yes. Both are legal requests, if you want to think of it that way. But types of requests can be differentiated. We can draw a distinction, for instance, between a charity requesting that you voluntarily donate $$$ and an armed man on the sidewalk pulling a gun and requesting $$$. :)

That's not correct. You can only request "non-content" data with a NSL, e.g. IP addresses, times of access, headers, etc. You need a warrant if you want actual content of communications, etc.

(that's legally, of course. Many companies will roll over for even an informal request if they don't know better or to play ball (see: the telecom industry))

The fact that there is no judicial oversight, and thus almost no paper trail, is the real problem. They may not be completely different; they are different enough to be a cause for concern.