You may already be aware of some Nebraskan exceptions. It is the only state in the US with a unicameral legislature, and is one of only two states (along with Maine) that splits its electoral college votes in presidential elections. Those are interesting, but I wanted to investigate the name of this blog post itself: "Except in Nebraska".
It's an innocuous phrase on its surface, but I associate it with this clip of Steve Ballmer:
I know what you're thinking. "What the hell did I just watch?"
Let's get one thing out of the way first. This is a parody, not a real ad. If you're familiar with Ballmer's other energetic outbursts (like developers developers) you might hesitate, but rest assured it is fake. It was presented at an internal Microsoft meeting purely for employee entertainment.*
Ballmer is channeling the overexcited energy of real commercials, in particular those for Crazy Eddie—see this real commercial from the same year. But what's that bit at the end, the "except in Nebraska" line?
There are two layers to this answer. I don't have complete, technical explanations for either layer, but here is what I found.
* Former Microsoft employee Ken Gregg explains this here.
The first layer is relatively straightforward. Ballmer is referencing existing commercials that themselves claimed to be valid except in Nebraska, sometimes using other language like "Offer void in Nebraska". The whole video is a parody, so this line is thrown on at the end as another joke.
Why were so many offers invalid in Nebraska? The best explanation I can find is that there were technical limitations on certain phone calls. Specifically, the call routing for 1-800 numbers could not simultaneously work for in-state and out-of-state calls. Because so many call centers were based in Nebraska, most 1-800 numbers didn't work from inside the state. Offering a separate Nebraska number wasn't worth the hassle for many companies, so they simply ignored the market until updates to the phone system in the early 1980s enabled in-state call routing.
The second layer is more complicated. Why were so many call centers based in Nebraska? Again, working on the best information I have: it started with the designation of Offutt Air Force Base as Strategic Air Command—Nebraska is centrally located, a positive for reasons of security as well as speed of communication to all parts of the country. To ensure availability, the government requested an enormous amount of phone capacity to be allocated nearby for future use.
This additional capacity went mostly unused until the 1960s, when AT&T began selling it to Omaha-area call centers. These call centers had many advantages: because of the excess capacity, phone lines were cheap and could be provisioned quickly; Nebraska's central location meant calls to either coast were cost-effective; the neutral accent of many Nebraskans works well for speaking to people across the country. The proliferation of call centers eventually led to widespread 1-800 numbers—numbers that didn't initally work in-state, as mentioned above.
Most of the sites I found discussing these historical notes are anecdotal and don't have true sources. I started researching from a Reddit post and a TVTropes analysis. The best article from a genuine news source that I could find is a 1982 UPI article. I also found corroborating evidence from this 1992 Washington Post article and this Aksarben Foundation page.
At minimum, I think the information presented here is directionally accurate. The designation of SAC led to large phone system capacity, which led to call centers, which led to Nebraska disclaimers due to technical limitations, which led to Ballmer's joke in an already-joking video. I was initially wary that this story was being repeated without true sources—sometimes a reasonable-sounding guess makes the jump to common citation despite the lack of underlying truth—but I think there is enough evidence of the overall patterns at play here.*
One final note. I found a high-quality version of the Microsoft 1.0 ad. Funny enough, I think this version lacks something. Maybe old commercials, even parody commercials, were simply not meant to be seen in high definition.
* You may have heard that the original translation for Pac-Man's name was going to be "Puck-Man", in part because the character is shaped like a hockey puck. Drew Mackie discusses the details of this claim on his blog, but in short: while Puck-Man was the original translation, there is likely no truth to the hockey puck claim.
If you have any more information on the history of phone systems in Nebraska or any other topic covered here, please let me know, particularly if you can point me to books or accessible news articles. Thanks!