In ESB revisited, Rich Turner nails it:
What if I wanted to remove or replace my current ESB platform? Surely, this is more insidious than any operating system, development tool or other such vendor lock-in concern? Because each ESB is implemented in an entirely proprietary manner, with no guarantees that the messages transmitted across the bus are actually based on any form of open standard protocol, there is absolutely no guarantee that any technology offered by a company other than the ESB platform vendor will be able to communicate freely via the bus. So, not only am I held to ransom by the ESB platform vendor because I cannot easily replace one ESB with another, but I am also likely to only be able to integrate systems which the ESB vendor provides specific adaptors for. Isn’t this precisely what we’re trying to get away from?
I whole-heartedly agree. The only justification for the ESB-as-a-product concept is that without it, there would be no expensive middleware left for vendors to sell.
Not a problem for consultants, though :-)