Shore - eBay and Trademe have not been supplanted because there is a benefit to the wider market in having a common shared platform.
Accounting is not like that. While there have always been systems of use to a sizeable chunk of the market (MYOB, QuickBooks and Sage are good example) there are also many niches with specific accounting requirements and also many different markets with specific tax requirements. There will never be an accounting market dominated by just one software provider.
Turmeric - I have no doubt that Xero has good people at the top. My point was that the wider you expand the greater the risk of cracks appearing. And those cracks appear not at the top but around the edges. The discussion I linked to from the UK is an example of that. Gary Turner seems to have acted on it once it got attention in public but it seems UK accountants have been quietly drawing Xero's attention to it for a year or so and got no traction. Their perception was that resources were being allocated elsewhere and not being allocated to dealing with their issues. These comments were worrying - and it is certainly not the first time I have seen this sort of grumbling. These are the cracks Xero has to attend to - otherwise as it expands there will be more of them.
It is easy to listen to the hype and believe Xero really is different but it is the reality of what customers like and dislike (and whether or not the business generates cash flow) that ultimately determines the success of a company.