You look at Google and for them the platform and developers are secondary. API's are not only an afterthought (such as in Google+) but they are something that other people use, not Google.
They kill services and API's because they don't need them and it doesn't effect them - but it does effect the users. I can still run SimCity or Test Drive on Windows 7, which makes me, as a user, confident that Microsoft will never throw me under the bus. This means that if you are an IT manager, you can make multi-million dollar purchasing decisions knowing that the technology will still be around and supported since Microsoft use it themselves.
Google could kill any API, and they have, and it doesn't impact themselves because they don't use these API's themselves, but they are asking developers to.
Google will never become the Microsoft of the web until they start using their own API's and until they start respecting their customers with long-term support.
Things may change and a formally-promising product may start looking grim. At that point this decision may make that product's future seem more uncertain, but I'd expect uncertainty to be dominated more by the product's poor performance/grimness.