When I was in my first tenure-track position at University #1 and my husband was a postdoc thousands of miles away, we both applied for every appealing tenure-track position that was advertised in our fields. There were lots of issues to consider, including (1) What do we tell my colleagues at University #1?, (2) If my husband got a great job somewhere else and I didn't, how would we decide who would make a sacrifice?, and (3) If such a decision came up, how would we decide which university is "better"?
1. I was very open with everyone in my department about my plans. My colleagues understood, and many of them wanted to hire my husband on his own merits; there just wasn't a position (until we got offers elsewhere, and one magically appeared). Meanwhile, I worked really hard at University #1 and was a good departmental citizen. It was clear to all my colleagues that I was happy there and dedicated to my students and the department, but that I had to consider other options as well. I didn't worry about not getting tenure at University #1 because of my situation re. applying for other jobs -- I was getting grants (including an NSF CAREER award), publishing papers, had high teaching evaluations, and was an active participant in departmental and university committees. I had a positive recommendation at every yearly review, and at the big 3-year review. A university cannot legitimately deny you tenure if you are doing your job well.
My male colleagues routinely get offers from other places, negotiate a higher salary or whatever, and acquire more prestige for having done so. They do it because that's how you get more money and prestige. I was seeking other offers so that I could live with my husband, and I was fortunate to have colleagues who understood and respected that. An administrator at my current university told me that women faculty are more reluctant to go through the process of applying for jobs once they are in a tenure-track or tenured position because it seems disloyal and not worth the stress. I used to say no to requests from other schools for me to apply or let myself be considered for a job once I was at University #2 and had tenure. Now I think that getting other offers is one of the only ways to get real respect.
2. I have no idea what we would have done if my husband had gotten an offer somewhere and I didn't. University #2 initially said they only had one position (for my husband), and the week or so before they created a position for me was stressful, but it could have been worse -- University #1 was fairly quick to come up with a tenure-track position for my husband, so we knew something was going to work out for us.
3. I have been very lucky that all the places I have been academically employed have been 'good enough' to lead to other opportunities. There was a recent study about whether there really are dead end academic jobs (Roach Motel Colleges, Slate.com, http://www.slate.com/id/2142489/), and, if you accept the parameters of the study, I guess there are. I think it's quite possible to be happy at a Roach Motel College, though. My husband and I disagree about this (perhaps more on that later).
12 years ago