Realistically, as mynameishere points out below, they were able to get a jury to convict him because he was doing some genuinely nasty things -- things no half-sane person would do at work, including soliciting prostitutes. It looks like a terrible injustice when you carry it to the logical conclusion, but realistically you would not be able to get a jury to convict someone for twittering at work, nor would a prosecutor ruin his career by pursuing a case like that.
This is just another example of, "Okay, we found a bad guy, now what laws can we use to nail him?" I don't think it's especially uncommon, and it is one reason juries are so important: they're the first line of defense against the unreasonable application of unreasonable laws.
The problem is that for the set of "generally nasty things" which are not "illegal things" one shouldn't get a felony on their record. Fired, sure. Bitched out? You betcha. But not a felony.
Because, see, letting people decide that things they think are nasty should be felonies and convicting people based on laws they've fished out to abuse for those purposes is ungood. You don't want that in a free society.
On the other hand, you don't want people violently breaking the social norms in a structured environment like a work place. That's why there's a whole range of appropriate remedies that do not involve the courts.
That's a good discussion to have, and I tend to agree with you, but my point remains: nobody is going to get locked up for checking the weather at work. There's nothing to justify the Redditesque hysteria being eagerly upvoted on this page.
I think this resonates with some because the line is unclear. I've had boobs show up on my work machine before when I followed innocent seeming links. Heck, last week one of my new twitter followers was porn spam that had a full frontal nude as a profile pic.
Where I live prostitution is legal (though I personally find it rather icky). I don't know what my response would be to co-workers looking up info on a brothel at work, but it wouldn't be to call the police.
When I worked at SAP of all places, on their list of entertainment venues in the area of the headquarters, one of the links on the intranet wiki was to a gay club that has dark rooms. If an SAP employee in the contested jurisdiction clicked on that link, would they be a felon?
This guy was clearly over the line, but I'd find it hard to say exactly where it is. If what he did made him a felon, I'd be hard pressed to say where the line is between him and the cases above. Since only one of the "nasty" activities that he committed was illegal (and that not even universally in the US) it is chilling that the legal system was rigged to find a way to convict him on a serious count that was put in place for entirely different reasons.
The guy was slammed with 3 counts: for soliciting prostitution (misdemeanor), stealing time from work (felony), and 'unauthorized computer/network' use (ie, 'hacking', also felony). They thoroughly nailed him with a misdemeanor and a felony which are arguably reasonable, hence there's no need to apply a computer hacking law in a plainly unreasonable way.
As applied here it means that any use of a computer "beyond the scope of the express consent" is a felony. Twitter and ebay use at work could be felonies under the same reasoning. I understand juries are a safeguard against unreasonable laws (go founding fathers), but I'd sooner have reasonable laws to begin with.
This is just another example of, "Okay, we found a bad guy, now what laws can we use to nail him?" I don't think it's especially uncommon, and it is one reason juries are so important: they're the first line of defense against the unreasonable application of unreasonable laws.