While I was at Google one insight I had is that there's a copy of most internet products. Given the cadre of college grads they hire to work there, cloning something is almost like a fun little coding challenge.

Dropbox? There's a clone. Pinterest? Clone. Everything. Then they dogfood it and if there's more interest they gather up more resources to inevitably pitch the idea to Marissa Meyer, who then plays with it, design the business case for it, and approve a proper budget for it.

If the product is good then the news leaks or they launch it. After awhile if the Google audience doesn't like it they cut it loose.

Which goes to say... any time some investor asks you what happens if Google comes into your space, you should say: good.