I think that, like many things, there are no easy rules here. I agree that short is an advantage, but not an absolute imho. One point from the podcast (see below) was that an unusual spelling (like Lyft) is easier to deal with if the name is short. A name that is both long and unusual (e.g. made up word or wrong spelling) is a big negative, but one or the other is manageable in many cases.
With sufficient marketing might and dollars, almost any name can be effectively used. We certainly have cases of words which are not easily spelled (Lyft or Flickr), not simple (AirBnB), not short (KitchenAid), not inherently related to the operation (Apple, Amazon), etc. that have been hugely successful as brands.
By the way overnight I just listened to the
latest DNW podcast which is with Eli Altman (he is second generation in naming, his father started the company) at
A Hundred Monkeys and is about corporate naming. A few points that stood out to me - normally they have a two pass system with 600 + possible names during the first pass! He said that while they educate end users re domain prospects (like typical cost if you want a short correctly spelled word in .com) the domain availability consideration comes later in the process and they do not even at second stage consider it too much. He also mentioned that corporate leaders are increasingly open to other domain possibilities, including alternative extensions if their preferred name is not available (or not at a cost that they can afford) in .com. It is a great listen.
In my mind the one absolute in naming is that it should evoke
positive feelings (or at least not negative ones). The podcast guest I guess suggested another absolute, or near absolute, is that the name is
not boring.
Bob