Anyone with a generator, large or small, could potentially compete with the incumbent local utility by creating his own transmission lines.
When incumbents own the whole existing system, from generators through transmission and distribution grids to the consumer, the barriers-to-entry are raised if someone with a generator also needs to create new transmission lines. Its also inefficient duplicating infrastructure, and the new-comer is at a disadvantage negotiating connection to the distribution grid, when that is owned by the same incumbent that owns the competing transmission lines.
Where I live, the local government power utility was privatised and split up into separate businesses for generation, transmission and distribution/retail - with the government currently the majority shareholder. Although some people believe the transmission-business costs are inflated, such that the generation-business runs at a loss, which makes it harder for other generators to enter the market - overall it should promote future competition at the generation level. My (partial) belief is that grids should remain govenment property, but operated by a contracted private company - which can be changed as performance requires.
...competition among telephone, data, and cable companies,
The emergence of entrepreneurs who can lay down their own grids as a matter of right...
Its going to get awfully cluttered. Who is going to co-ordinate this, to avoid clashes and enconomical routing. I've been considering for a while that what is required is a bundle of underground culverts and conduits that are government owned, and the space within is leased through an open-bid auction process - which would eliminate the grey-wolve process - to let the market decide what that space is worth. Right of ways, particularly in urban environments, are a scarce resource. The problem with granting them to private individuals in-perpetuity is that in 50 or 100 years time when technology changes or the incumbent becomes defunct, then it is hard to recover these right-of-ways for other uses.