Picture the scenario:
The user has their own laptop as they must have the latest in style, portability etc. That device then has a hardware failure. Who is now responsible for ensuring that user can continue to work. In a coporate environemnt the device will be swapped out quickly. Fo the home user it has to be packaged up & sent backup for repair, assuming that it is in warranty. This is suddnly an IT issue again as the user is unable to work for an unknown lenght of time.
Similar issues are evident in the software. The device is suddenly unusable because new home software is installed that is stopped something else working. What now, once again the user cannot work but it is IT's problem to sort it out. There is now a home laptop with a 1TB drive filled with personal material. Options are limited unless full backups are taken or a disclaimer is signed by the user that all data may be lost. Depending on the setup this also may have coporate data scattered over it.
The final point, device needs replacing & the user now decides that because they use it for work, the company should contribute to the cost. More admin and increased costs.

BYOD is invariably driven by managers who have to have the latest toy and bypass everythign to get it. It is not a buiness need but status.
Yes Citrix & other VDI type of solutions can help however to secure the environment but in many ways they have to be mandatory. Any other solution that relies on local installation of software is a security & compliance disaster.

Who are the winners from this?
Short term is the company balance sheet as workstations do not have to be replaced
Resellers and the likes of VMware and Citrix in licensing
Short term feel-good factor for the users.

And the losers?
The users themselves once they understand the implications of using thier own hardware.
The users when they now discover that they are never out of work. It is bad enough with mobile email out of hours or worse on holiday but add to that full office functionality and the pressure will be there to always do that bit more. In the UK statistics already show that UK works put in more unpaid time than elsewhere.
IT Departments supporting the resulting mess of hardware
Compliance & governance teams trying to keep track of the data & inventory of where stuff is.;