I have worked in both public and private sectors (including on projects which assessed employees’ time spent on various activities including sick leave), and not noticed any major problem with unplanned sickness absence which could not be combated by better management practices.
These are simple remedies, such as ensuring all team members are aware of everyones workloads and progress and there is enough contingency resource in a process, so deadlines can still be met and a customer is not inconvenienced by the lack of staff.
I think its a very minor problem that has been grossly exaggerated by those with a political agenda (mostly conservatives who do not believe in the protection of workers rights).
As the TUC said, most people who are off sick genuinely have something wrong with them.
In many cases it has in fact been caused by their employment, either by stress [particularly with the lack of secure jobs and constant threat of downsizing/outsourcing], badly designed office buildings and infrastructure, or exposure to dangerous substances or other contaminants used in the workplace, with safety procedures sometimes having corners cut in order to speed up delivery or save costs.
Its also true the boss who “bravely comes in to work” is probably contaminating his/her entire team and risks further disruption due to absences.
That said, on our scene there is a minor issue with (mostly younger) people calling in a “sickie” after caning it too hard at the weekends – a lot of employers become suspicious when people are not there on Mondays (particularly if more than one person from a team is off and they are known to be friends) – that has led to stuff like workplace drugs testing, return to work interviews with nurses and all the big brother stuff.
Most HR departments know damn well about “ravers flu” and that in an otherwise healthy young person a large amount of respiratory tract infections or other minor bugs can be caused (or made worse) by drugs/alcohol use – there have been various consultancy companies set up to tell the bosses all about this 🙁
If you rave and find you need recovery time its perhaps better to plan your partying so you can get time off if you’re really gonna go for it or be prepared to calm things down a bit or even leave earlier so you can get sufficient sleep etc – its also better for you in the long run!