I think that in most cases Google will interview the employees of the company to be acquired. Either in advance to decide whether the company is worth buying at

I think that in most cases Google will interview the employees of the company to be acquired. Either in advance to decide whether the company is worth buying at all, or after the fact to decide who can keep their jobs. The bar might be set slightly differently in these cases than for normal hiring, but certainly not so different that the vast majority of the acquihires would have been "miserable failures" otherwise. (Also, I've never heard of G+ being in any way a product of a talent acquisition.)