"Best Practice" is the latest trend in IT and business process management, what are the disadvantages of best practice?

Best practices might not become relevant due to different culture or way of doing business in some places. So some time you have to change and adopt according to local environment. 

Best practice pros and cons are subject to the environment, culture and industry you're dealing with. 

AGREED WITH HASEEB KHALID

Best practice is the success result of academic theories and real achievements , but in all cases  you must consider the differences in the environments and other factors in ur local place and where this practice was. It means that best practice never was cut and paste

- Not matching the local requirements.

- Increase costs and erodes profitability in local markets.

- Conflict (or not required) by local regulations.

- Not understood by the local workforce and no training takes place to cover the gap.