We have a standard way of approaching spousal hires. Whenever we get a spousal request (and we get them a lot), the first step is to review the CV. At this point we're looking to see if this is someone we would be likely to shortlist in a full search. If the answer is no, then we decline the request (and we do this a lot, too). If we like the CV, we take the candidate through the usual process of interviews, job talk, etc, and then we vote, as we would in a standard hire.
We haven't had a spousal hire recently, because money at the university has dried up, but there are two people in the department who were hired through this procedure. We're not, as a group, in agreement about whether there should be spousals at all, even with the procedure described above, but I can truly say that the colleagues in question are thoroughly integrated into the department, and have proven to be real assets.
It doesn't always have to lead to a bad situation, in other words.
A spousal hire was recently thrust upon my department at the university where I'm a grad student. The department called an emergency meeting to protest it. Can a spousal hire be imposed from high above?
This usually happens when it is the spouse of an administrator. Why was the department protesting it, though? Were they were forced to bear the entire cost of the line? If that's the case, they're right. Otherwise, they could be getting a new line for half or a third of the price. It sometimes amuses me that people who consistently complain about lack of hires, high teaching load, etc. will refuse a hire for 1/3 the price of a regular line, because, essentially "it wasn't my idea". Gift horse in the mouth and all that.
However, while I am a big proponent of spousal hires, the point of a spousal hire is that it is the price of retention of an individual. Therefore, the entity which wants to retain the individual should bear much, if not most, of the cost.
Now, if indeed we are talking about the spouse of an administrator, well, the fact is that most administrators stay in their job fewer years than it takes for a person to get tenure, so if the hire turns out to be a doozie, well they will be denied tenure. On the other hand, most of the spousal hires that I've known have been very successful, publishing well, bringing in grant money, etc...