Since this blog is called the The Grey Lines I would be remiss if I didn't point out the greyness in Joe McKendrick's latest post on ESB's. I certainly understand where Joe is coming from but this is one of those grey areas. SOA is not about the technology, I think that has been beat to death by now. However developing a service and implementing it still requires technology. I'm doubting the enterprise in question chose the ESB route simply for the one project.
There is the belief out there in the distributed nature of an SOA style of implementing services ie location independence, technology agnostic etc etc. I don't disagree with that and designing services should certainly take that into account. However in the enterprise decisions have to be made on technology implementations. The fact is one size does not fit all. While one enterprise may go to distribution (very strong governance needed here) another may find a more centralized platform (governance still needed but not as strong) works better for them.
Decisions have to be made every day in the enterprise that involve compromise. It's just the nature of the beast. I think understanding how your own enterprise functions is a key to picking the right implementation strategies. I know most folks would say SOA is not about the implementation but ignoring it will lead to disappointment with your SOA style of architecture.