I don't remember anyone saying Uber/Lyft/Airbnb were toys when they began. Some might have thought them unlikely to succeed, but that's not the same thing as being a toy.

I do not think we are referring to Toy's literal meaning here. IMO, Toy here means something insignificant that a few people/small market uses.

Exactly. Those of you that are hung up on toy meaning a literal toy or video game with no intrinsic value can replace the word toy with "gimmick" or "novelty" or even "a serious idea that won't scale" (http://paulgraham.com/ds.html).

Early Air Bed and Breakfast charging people for couch surfing and selling Obama O's (https://www.airbnb.com/obamaos) to fund their startup definitely feels toy like to me.

I'd argue there are entire categories that are currently considered toys, but eventually with the right business model, tech improvements and cultural changes will make the serious billion dollar tech companies we have now look like toys.

Toy vs Tool means novelty vs efficiency creator. A toy is fun to use it exists to be used for pleasure, a tool is useful and exists to make work easier. Toy should be used to mean superfluous bonus, unnecessary but enjoyable pastime.