I think it's a little early to tell if it's a failed product. It might be in terms of unit sales, but I'm sure that in terms of the knowledge and understanding of AR, Google are probably in a good position to capitalise on the (hopefully) coming AR/VR wave.

Did Windows Mobile help Microsoft capitalize on the Mobile revolution? A too early product doesn't always help you capture the value of coming wave.

Google Glass isn't a product yet, so it's unclear how it could be a failed product.