Came across a couple of posts by Joe McKendrick's on SOA and reusability and he has an interesting conversation with a couple of other blogger's specifcially David Chappel and Harry Pierson....Below is excerpts from all thier posts that i found interesting,

Is reuse an idea that's too good to be true?

David Chappel seems to think so "the "reuse" concept didn't work too well with object-oriented programming, and isn't working too well with SOA, either." He also goes on to say that "despite heroic efforts from many IT managers, architects, and developers, the cultural and business barriers to reuse were just too great."

The 'If-you-build-it-they-will-come' approach is tough to turn into real reuse,"

Creating services that can be reused requires predicting the future

There are a few areas where reuse is working one such area according to David Chappel is "Integration"

Gartner - "should expect to reuse only a fraction of your services, maybe just 20% of them."

Common Issues that are being faced are:

• Creating services that can be reused requires predicting the future.
• If an application does expose a useful service, it's rarely exactly what the client wants.
• Even if one part of an organization does create a service that could profitably be reused by some other group in that company, the manager who owns this application usually doesn't have much incentive to let this group consume its resources.

"When someone mentions the idea of using SOA for reuse, I cringe..." -Harry Pierson, Microsoft

Erl's (SOA consultant and author - Thomas Erl) view is that "if an organization does an appropriate top-down analysis of a well-defined business domain, it's quite possible to discover and implement reusable services." David agrees with this argument, but Erl was not able to entirely sway him: "What's harder for me to believe is that a majority of organizations will be able to do this. Instead, I've come to expect most efforts to take a more technically oriented bottom-up approach." He notes that vendors will be forcing enterprises to adopt SOA, with or without reuse benefits.

The only true candidates for reusable services "will be the ones with little or no contextual needs," such as directory services, management and operations, business activity monitoring and provisioning. "I actually think there will be less reuse in services than there was with objects," Pierson concludes.

These thoughts lead us to the fundamental question of - Than what is the real value SOA will provide?

Converging trends and business necessity - above and beyond the SOA "vision" itself - may help drive, or even force, reuse.

Given that the coming wave of vendor platforms will all but force us to build service-oriented applications, it will be hard to avoid at least this much SOA.Will this simpler, less ambitious approach offer all of the benefits claimed for SOA? Certainly not. But is it an improvement over the world we live in today? Just as certainly, the answer is yes.

Source: 1, 2, 3, 4, 5