Along with the unveiling of prototype handsets using Google's Android mobile application development platform at the Mobile World Congress in Barcelona, came the promise -- one more time -- of write once, run anywhere.

And while write once, run many gives application developers a maximum market for their applications, industry experts have their doubts that Android or any other mobile solution can fulfill the promise.

Bob Egan, chief analyst with the Tower Group, points out that differentiation often takes place at the hardware level, such as optimizing battery management or display characteristics.

Anthony Meadow, principal at Bear River Associates, a leading mobile development company said the ability to achieve write once, run many depends on how the hardware and software developers do their respective work, the problem being that everyone wants to be different. "How can a hardware manufacturer differentiate their product from everybody else's and at the same time be compatible with the standards they want to set?" he said

Making it even harder to achieve standardization is the plain fact that handset manufacturers are not standing still. New features are constantly being added. Offering music downloads, pictures, and video is practically old school. Now, handset manufacturers and the carriers are talking about new security features like embedded security credentials for a boarding pass or entry to a company, or loading loyalty cards.

"When you start thinking of taking handsets to the next level, there is a whole new set of complexities," said Egan.

So while a cross platform mobile SDK would be welcomed by developers, especially Google, which needs to put its services on as many devices as possible in order to grow, the hardware subtleties are the things that come up to bite people, adds Egan.

Meadow at Bear River admits that if Google had a tough certification program, it would be possible to get much closer to the write once, run anywhere prize.

Google certainly has a great deal of clout in many parts of the high tech industry, but is it powerful enough to make demands on the telecommunications industry as well? Both Microsoft and Palm tried that before with very stringent certification processes for their platform. But it never really worked. "They couldn't keep everybody in line," said Meadow. "It was a lot more pain and trouble to get J2ME apps running on different cell phones."

While the Open Handset Alliance [OHA] -- founded by Google -- is touted as the way to get many companies on board, in fact there are only four handset manufacturers who are members: HTC, LG, Motorola, and Samsung.

Tower Group's Egan says he hasn't seen anything out of the OHA to indicate it's doing anything different than what has been done in the past.

Meadow doesn't put much faith in the clout of the OHA either. "People join everything that comes along. It is an exercise in PR to be seen as supporting this and being associated with Google," he said.

So while a write once, run many platform is the holy grail for developers, if you look at what happened with J2ME on smartphones, there were inherent limitations in how it was implemented as a platform, and for many developers it was a lot more pain and trouble to get J2ME applications running on different cell phones than it was worth.

While both Egan and Meadow are withholding final judgment, they both say they haven't seen enough that is different -- despite that fact that this is Linux-based rather than Java -- to make them feel any more positive about Android's future success.