I presume theyre not 'publishing' what the illness or excuse for being off sick is? If theyre just saying that Joe Bloggs was off sick 5 days this month I can't see anything wrong with that as it is stating a fact - and the people working with Mr Bloggs will certainly know that he has been off 5 days anyway as they will have been covering for him.
Most employment contracts will have a clause concerning sick leave which will allow the employer to, as a last resort, terminate a contract due to poor attendance, which can include sick leave. They would need to keep this in proportion though as it would be seen as grossly unfair if a person was disciplined for having one day off sick.
Employers are advised to do return to work interviews after any sick leave (even one day) as this action alone tends to cut down on the number of sick days taken. This would be most employers first step with perhaps disciplinary action for those that appear to be serial sick leave takers.
I cant see a problem having sick leave charts, the same as most offices have annual leave charts. There would probably be a problem if they gave the reason why people were off i.e. their illness, as this could be a breach of confidence.