Commercial property is constantly being labelled as 'no longer viable' and then converted to flats. The thing about the viability of a business is that it is highly dependent on the rent being asked for the property it leases. If there wasn't any prospect of change of use being granted, then the market would find the right price for a commercial unit, the point at which the business would be viable. The truth is that there is significantly more money in residential property. During a recession say, many businesses may find that they are 'no longer viable'... but that's not to say that 5 years on a similar one may well be. But once a commercial property has passed over into 'private residential' it is rarely going to travel back the other way again. What this means in practice, is that over time, we get lower and lower amenity to housing ratios. Amenity ends up reflecting demand as it was during it's lowest level in any given area. The reduction in the number of cheap commercial properties is a barrier to entrepreneurism. It's leads to clone high streets, lack of creativity, lack of dynamism and an unbalanced economy. Councils can't bear for there to be boarded up shops or offices (and property speculators play on this), but sometimes leaving a property empty can be preferable than loosing it's commercial potential for ever.