This is based on my personal experience as well as those of my classmates.
Most of us had a clear idea of what we wanted when we set foot in LBS. Most of our CVs were amongst the top 5% from our respective countries, so our thought process was like this: ‘of course we’d get what we want’! Why then, does the class of MiFFT2013s, cream from their respective countries, have 50% still job hunting, even after 3 months post graduation? What didn’t go right for most of us?
One side of the coin: Fewer jobs coupled with current oversupply of talent in the market and competition from peers. The visa situation also adds to the woes, with many companies cutting down on visa sponsorship costs.
The other side of the coin: Some jobs, particularly trading ones, require language skills with banks/trading desks expecting you to bring in new clients immediately upon joining. Some other jobs, particularly asset management ones, need you to indulge in heavy networking right from the beginning, which is then likely to convert into a job with time, perseverance and hard work.
Yet another dimension: For most of the students a career change now means they can’t get back to what they were doing prior to LBS neither can they think of shifting sectors again. Thus they have to be doubly sure of whether a career change is the right option.
Even to a person with very little background in mathematics this seems like a linear programming problem with several (severe 
) constraints, objective being DREAM JOB! No wonder it is taking time!!!
) constraints, objective being DREAM JOB! No wonder it is taking time!!!