I've read a bunch of other lists like the one I'm about to present, and they vary according to tastes. For example, one list cited the lack of games like FarmVille-- an absence that I would rate as a selling point. So I don't expect everyone to agree with my priorities, but here goes:
Google -1: Search
How did Google manage to put out a product for which keyword search is one of the most prominent missing pieces?
There is actually a search bar at the top of the home page, but currently it's a Find Friends feature. Congratulations, Googlers, on putting people first! But if I want to know who has been posting notes about Google+ shortcomings I have to step outside G+ to google.com and do something like site:plus.google.com missing features in "google+".
This works, but it kind of misses the point in that it only nets the posts set to public and not the ones sent to a restricted circle of friends--even though I might be included in that circle. Puzzled though I am about why this would be the feature they would leave out (even at this early stage), I suspect that it's the privacy and sharing rules that are holding things up. Maybe we'll all be impressed that they've got it right when search for Google+ finally arrives. The help docs put it in the coming soon category.
Google -2: Hashtags
Hashtags would make it easier to search for posts that are actually intended to be about a particular keyword, as opposed to those that just happen to contain it. And clickable hashtags as they are presented on Twitter provide a convenient way of navigating to related posts on the same topic. Remember when #egypt spread over the Twittersphere for conversations related to the Tahrir Square protests?
The creator of the hashtags as an ad hoc means of grouping content on Twitter is Chris Messina, a Google employee whose title is Open Web Advocate. Messina is advocating for the adoption of hashtags or something like them. He personally has adopted a convention of listing a series of hashtags at the top of his posts as a way of telegraphing their content, even though Google+ doesn't automatically turn them into links.
Google -3: Google Apps Profiles
Lack of support for Google Apps accounts (which exist in a parallel universe to accounts for Gmail and other Google services) is an annoyance for many Google Apps account holders, including paying customers. It's high on my list because I own a small business domain that's associated with Google Apps, which is where I'm logged in all day for business email. Google won't allow me to have two identities logged in at the same time, so I have to keep Google+ open in a separate browser where I'm logged in with my old unloved Gmail account.
This awkward arrangement is keeping me from being quite as enthused about Google+ as its biggest fans.
Google -4: Introductions and Re-Introductions
One of the nice things about LinkedIn, at least when people use it properly, is that you get introductory messages reminding you where you're supposed to know them from, where you both worked or did business with each other, or what interest group you have in common. Ideally, that comes with a personal note saying why you should connect.
The Google+ model of contact circles is like a better categorized equivalent of following someone on Twitter, so you don't have that "will you be my friend?" or "I'd like to add you to my professional network" thing going on. Still, when you add someone, it would be nice to give them a little context on where you're coming from (without them necessarily having to click through to your full profile) so they have a clue why they might consider adding you to one of their circles.
I know I'd appreciate getting a clue on incoming connections. Otherwise, I'd be stuck with limiting my circle of friends to people I actually know, and who wants that?
Google -5: Clutter
Just kidding. I've looked at other lists of missing features, like this one from Business Insider, and find I often don't miss the same things other people do.
Ultimately, the strength of Google+ may depend on what its designers have the courage to leave out in order to keep it slick and simple. If they crammed in every feature people are asking for, they would wind up with something hideously complex.
Even the decision to leave search for later strikes me as kind of courageous, as if it were Google's way of saying, "we're not going to lean on that crutch and build a social network around search--we'll build it around people."
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