Does the employer have to own the PC?
When I first started working in 1983, PCs were very expensive (relative to salaries), and their corporate software products were likewise pricy. Of course the company had to buy them and make them available for employee use, just like office furniture.
As laptops were introduced in the early 1990s, the price was still very high (relatively speaking), but the portability and the value of portability became pretty clear. Later, as the performance rose and the price dropped, it became clear that consumer PCs were an entirely new marketplace driving processors and graphics cards and sound processors that would be useful for business, but couldn't be the driver.
With the emergence of the Internet in 1995 (it was commercialized that year), the shift towards consumers as the initial target for innovation became really clear.
There is a lot more than the machines that have to be considered.
What about support?
Fast forward to today, and we see clearly that consumer PCs are higher performance machines and that there is a well-established, standardized and inexpensive consumer support service. AppleCare for example offers extended warranties, Apple offers Genius bars in their stores to consult with customers, Geek Squad is integrated into BestBuy and Fire Dog into the Circuit City retail experience. Regardless of brand, employees can find support for PCs within a typical mall shopping distance.
My daughter works in the television production industry and they form, dismantle and reform ad hoc production companies. In the TV business, the skilled editors, assistants, production crews and producers are assembled on an ad hoc basis. Employees have to purchase their own computers, purchase their own software licenses (office and or any special purpose software) and arrange for their own support service in the event of technical problems.
Corporate email addresses aren't very useful because these are such special purpose and short-lived organizations. Telephone, WiFi and internet services are provided (so most employees, except field crews pay for their own mobile bills).
Users are paid between $20 and $37.50 per week for the corporate use of their computers (depending on the practices of the company). Since it's the employee's own computer, they'll care for it better than a company provided one. They'll upgrade it more often and local consumer support service is probably cheaper and more easily obtained for remote employees than the centralized support of most organizations.
So, to answer the key question – should employers own the PC? – the answer is no.
Since the standard elements – email, anti-virus, anti-spam, web browser, Microsoft Office / Lotus Symphony / Google Applications / Star Office, VoIP softphone – are all readily available not to mention the support service, this model makes a lot of sense to me. I fully expect more and more companies are going to go to the virtual PC provided their concerns about information security can be addressed. The Google Apps approach of network-stored content may be the answer for some.
