It's a funny business, this references lark.
When I (unsuccessfully) applied for an MA last year, I asked an UG tutor for a reference back in late November/early Dec, received confirmation he'd oblige a few days later...actually received the thing, after plenty of chasing (embarrassing when it is your ex-tutor), in late February! The plan had been to get my application in by mid January.
The same referee did agree to provide a further reference this year however, so I duly asked again a couple of weeks ago: no response...which made me think
ugh or, in smiley terms, probably

...here we go again.
My girlfriend, who is applying for different MAs, has had even worse luck...a series of (fairly blunt) refusals from ex-tutors.
So just wanted to ask you all your views and advice on the referencing process.
How long should students expect to wait?
Are certain times of year less reasonable than others?
Is obligation to provide them only 'implied' or a defined part of the tutor's job description?
Is the content, and therefore choice, of reference actually more important than the general 'seal of approval' that any reference from the same institution would carry?
Also, are references really a fair and accurate basis on which to judge an application, assuming some level of 'doctoring' can be involved and given that the obtaining of the references is often down to the organisation and attitude of persons outside of the applicant's influence?