Though Google says it decided to end Glass sales and the Explorer program because Glass has "graduated" from its research and development status, some of even the most devout Glass fans are expressing concern the wearable has been grounded for good and may be headed where many other Google innovations have gone: the Google crematorium.

But those speculating on the future of Glass may need only to look back on Google's past to understand why and how the search company made its notable decision to stop selling the controversial eyeglass computing headset.

Here is a quick look at some past Google innovations sent to pasture.

Google Notebook

Google Notebook stuck around just long enough for Evernote to emerge and take over the digital note-taking sphere. Google Notebook lasted six years before the plug was pulled.

Dodgeball

The acquisitions of YouTube and Android illustrate Google's foresight, but something went wrong when Google purchased location-sharing service Dodgeball. After Google's fumble with Dodgeball, the company's founder took leave and went on to create the well-received and successful Foursquare.

Google Wave

There's no need for any tech savvy individual to feel bad if Google Wave doesn't spark any recollection as even Google wasn't sure what to do with its social networking platform. Google Wave was successful in confusing users for about a year before Wave washed up on unknown shores and has not been heard of since.

Google Video

Just shy of two years into its development, Google's failed attempt at video hosting was quickly replaced when Google acquired YouTube. What some may not know is that Google Video actually remained active for several more years before fading into oblivion. But it's clear that while Google was late to the streaming video sector, its acquisition of YouTube was brilliant.

Google Answers

Google found itself one of the last to move into the "answers" business, but it makes complete sense the search company felt it still had a big competitive edge, given it was a leading search engine providing millions with answers every day. Yet the execution of Google Answers proved weak and flawed and ultimately the tool was shuttered four years after launch.

Resting in Purgatory

Google's purgatory is well-populated with Google Plus, Google Checkout and Inbox, some of the products being put to rest. Yes, Inbox fits in that category despite that it's still undergoing testing, as early user feedback already reveals it isn't quite addressing the needs of power users. It's a fate Google Glass could very well find itself sharing unless Google finds another entity to carry the wearable torch forward.