Extended version of this post, cut from the end.
In any given job search, the perception of whether or not there is a general librarian shortage is fundamentally irrelevant. It all comes down to which individuals apply for a position, and which one comes across as the best fit. I've been on the other side of hiring for library assistant positions and have seen four different outcomes.
1. Strong applicant pool which resulted in a good hire.
2. Weak applicant pool which resulted in a good hire. The other finalists were very unsuitable, but that didn't matter because the person we hired was excellent.
3. Weak applicant pool which resulted in a not so good hire.
4. Strong applicant pool which resulted in a not so good hire. Combination of the successful candidate being very skilled at interviewing and a possible mistake by the selection committee.
Even if there were shortage conditions and the pool of applicants wasn't as numerous as an employer would like, it only takes one better qualified candidate to beat you. And as Meredith mentions, it can be difficult to really know why that happens. In one instance, somebody had the best qualifications on paper and who also came across well in the interview didn't get the position because s/he seemed very similar to somebody who hadn't worked out before (the one mentioned in number 4). Was this decision made for the wrong reason? The person we ended up hiring was a great asset to the library.
I guess the point of all this is to illustrate how there are no certainties in the process - librarian shortage or not. Not only is the librarian shortage erroneous (at best, premature), but it would be irrelevant to most job seekers as well.