Yes we need it. That shouldn't even be a question. Did we need transistors? Did we need the keyboard, the mouse, the gui, the network, the Internet, modern web browsers, tablets, cell phones?
Are we ready? No. I do not believe so.
We are not ready for google glass on at least two fronts: privacy and self control.
Are you mad about google+ integration? Ok, then do you really think google glass will continue the trend of the ever watching google or will it reverse the trend?
Would you be ok with Google mining your "anonymized" glass data to build a better profile on you? Would you be ok with Google mining someone elses "anonymized" glass data to build a profile on you?
What about when glass data becomes part of what law enforcement / the government can subpoena?
Are you upset when you try to install a flashlight app and it tells you it needs full access to all your contacts, current calls, and the network? Wanna bet that all google glass apps are going to want full access to your current location, your vision, your hearing, what you say, and who you are with?
We aren't ready to deal with that yet, because as a society we still haven't found a current level of privacy and usefulness that strikes a balance. I think that there is a balance, but as users of the devices/services we just don't have enough power or information.
On top of privacy, we just don't have the self control and awareness to not do stupid things online. It will only get worse if we start using always-on, internet connected wearable devices. And I'm not referring to anyone who uses social media and the internet responsibly, I'm referring to the people who aren't informed and aware of the implications of uploading something to social media or posting it online.
How often do we hear about some highschooler suspended/expelled because he/she said or posted something stupid on facebook. Something completely harmless but since it is out of context for all the world to see, there are consequences. Furthermore, revenge porn is now getting into the courts, and its not just an angry ex leaking a sextape that two adults made, there are tons of people that don't realize that chatting naked with a stranger on the internet is a really good way to have that video posted to every shady corner of the web. For ever. Videos and pics of drunk college parties are preventing people from getting jobs upon graduation because they never realized that posting that time you pissed off the balcony at your frat house would show up on some HR person's search of you.
We just haven't caught up yet as a society. That doesn't mean there are completely responsible informed people who would use google glass in positive ways, it means there are a lot of idiots who are going to do something stupid then cry when their life is fucked up because of something stupid they didn't mean to have broadcast to the world.
I don't think that means we shouldn't move forward with google glass, I just don't think we ready as a society to use wearable computing devices responsibly.