It matters both a lot more, and a lot less, for startups (than traditional companies). More: a startup doesn't have the resources to just throw bodies at a pro

It matters both a lot more, and a lot less, for startups (than traditional companies). More: a startup doesn't have the resources to just throw bodies at a problem, or have a dedicated dev or two working on a non-core product. Picking the wrong language + ecosystem can ruin a project. Less: Startups are make or break. If you break then who cares about the long term cost of code maintainance? If you make it then you can easily absorb the long term costs. E.g. If choosing php in the early days cost Facebook an extra 100 man-years worth of effort in the long term its a minor blip. 100 man-years is nothing to a company the size of Facebook.