Snap it, send it, move onADAM ROBERTS
Technology allows you to preserve moments forever, bolstering otherwise fleeting memories.
We've always treated this ability as a virtue, as a benefit, but perhaps it's not.
Twitter has the sense that its content will not last forever, with a lot of scrolling required to get back to the beginning of a user's feed.
This suits the nature of the service quite well - tweets have a shelf-life, after which it becomes difficult to unearth them, and so this keeps everyone more focused on the present.
When Facebook released Timeline last year, it was a shock to look back and see messages you'd posted years ago.
You were a different person then, and having those statements attributed to you felt wrong, not to mention embarrassing.
Maybe we should be looking for apps, services and devices with memories a little less infallible, forgetting our past sins.
Two new apps have shown illustrated the contrast between the old and the new approaches to chronology and forgetfulness.
The first is Vine, a video-sharing app owned by Twitter, that has been labelled "the Instagram of video".
Its interface makes it easy to quickly share moments with the world, allowing the user to record six seconds of video, which is then displayed in a loop.
You record by tapping and holding a finger on the screen. You can tap and hold as many times as you like for up to six seconds, so you can create jump cuts.
Once you've finished recording, the resulting short video will loop so you can have a look at it, and then you can post it to Vine's own social network, as well as to other networks like Twitter.
Editing and recording are intertwined.
The first Vines have ranged from stop-motion cartoons to people dancing to, well, porn.
But in the latter case Vine has acted quickly to hide many of the more unseemly elements of its new community out of sight, censoring searches for #porn and other similar terms.
But it is clear that with Vine, otherwise incidental moments are captured and repeated forever - like a smoother version of the animated gif, which has enjoyed such a resurgence lately.
Another interesting thing about Vine is despite its supposed amateur nature, the threshold for quality is somehow higher than it would be for a picture or video.
While I'm sure a set of norms will develop, currently Vines have a higher bar to clear to provide amusement.
Clicking on a link to a Vine means a six-second investment, probably longer, so it had better be worth it.
As a webcomic summarised it: if Instagram is "look at my sushi", Vine is "look at my sushi for six seconds".
Because the clips are so short, it's obvious that whoever uploaded it was aware of what they were putting into the world.
While YouTube is full of videos filled with amusing accidents, Vines are that much less spontaneous, and so have an uphill battle to charm.
But the central conceit of Vine is that these are moments you want to share with the world, and moments you want to keep forever.
Not so with Snapchat, another new-ish app which has also seen a rapidly growing userbase.
Snapchat is all about the moment.
The app lets you snap a pic, optionally draw on it, then send it to a Snapchat friend, who then has a certain amount of time after opening the message before it disappears from their phone.
The app initially drew criticism as being particularly conducive for a certain, x-rated, kind of message, allowing young people to 'sext'.
As a side-note: isn't it interesting that both of these apps, with different functionality and purpose, have immediately become synonymous with porn? Interesting and sad, I suppose.
Anyway, with Snapchat, moments are forgotten by the software even quicker than they fade from your memory.
Using the app is more like a real conversation than any other social app, and reminiscent of instant messaging before the services remembered your every utterance.
It would be great to see more apps and sites behave this way - forgetting material that's no longer immediately relevant. We may all feel safer using them.
The potential problem for a social network like Facebook, which for the most part makes its money from selling information to advertisers, is that this model could create less-valuable profiles to give away.
But would it? I haven't updated my basic Facebook information in years, and most of the favourite films and books I would have added then have been deleted as the network moved to new profile layouts and styles.
Even if that information was still there, it would doubtless be out of date, I've consumed a lot of media between then and now.
Such out-of-date information, as well as preferences chosen ironically, is one source of noise in social networks, and a potential problem for its services using them, such as Facebook's Graph Search.
So perhaps a social network that moves on with you and forgets the past would be more accurate, and more fun.
Given its popularity, maybe we're all ready for apps which behave more humanely. After all, what is more human than forgetting?