I had a sleepless night recently. The type of sleeplessness where your mind ticks over frantically, jumping from subject to subject. At about 5am, as I stared numbly at the dawn glow creeping round the edges of the Velux blinds, I tried to work out how old my internet bookmarks are. You know, as you do.

Back in the early 1990s my first computer was a Windows PC (the horror) without a modem. In those days I'd heard of the internet but hadn't actually seen it. In fact, nobody I knew had yet seen or experienced it. My first experience of the net would've been a few years later when I worked for a design and print business, a small studio sharing one dial-up modem between five people. I suppose I would've started bookmarking web pages then, but I would've abandoned those links when I moved to London late 1995.

The starting point would probably be when I bought my first Mac a couple of years later. Could that be right? I would've used Internet Explorer -- Safari didn't exist yet, and I'm pretty sure Firefox didn't either. Over the following 12 years or so I've had various new Macs and have always taken my bookmarks from one to the next. At first by exporting the links from one machine and loading them up on another, and then using Apple's old .Mac service. Recently bookmarking has been transformed by web 2.0 -- it can be variously social networking, life-blogging, an RSS feed, many filtered RSS feeds, a private online archive, or all of these at once. At the moment my bookmarks are synchronised by both Apple's MobileMe service (the successor to .Mac) as well as Xmarks. MobileMe keeps my bookmarks in sync across all my devices (work computer, laptop at home, iPhone) while the addition of Xmarks means everything is synced between Safari and Firefox too, so I can change to any browser on any device and all my bookmarks will be there.

But there's more. I also sync up using the Delicious plugin for Firefox. I can access my links on the Delicious website, or on the Xmarks site, at any time from anywhere in the world. This also means that -- in theory -- all my bookmarks are safe forever. I never again need to export awkward tab-delimited text files to transport links, and I never need worry about losing them.

But this isn't just a 'look how far we've come' story. Over the last roughly 15 years I've carried these links around with me. I might continue to carry them, and add to them, for the rest of my life. The way I bookmark (if I'm allowed to use the word as a verb) has changed in that time. I've organised and re-organised the links into folders and categories. I've weeded out dead links and updated them with new ones. I've tagged them with keywords and meta-data. I could probably find the date each of them was created and filter them in that way, creating a timeline of my browsing habits, looking for patterns of interest or changes in my life. There's something in this, no? D'you see it?

Of course the serious internet progressives and think-outside-the-box types have seen this already. That's how we ended up with things like social bookmarking, after all. And it will continue to develop. Other internet technologies will converge with bookmarking, and perhaps bookmarking will transform completely. But what I'm interested in -- what I pondered that early morning as birds sang and the milk float hummed past the front door -- is what does it mean to have all this information, both right now and decades from now, as it changes constantly, sketching a history of my internet life, amassing data-about-data, tracing my personality?

It sounds esoteric and trivial to say "let's talk about bookmarks", but there's a lot going on there. And to be clear: I'm not trying to give this a dystopian spin. I'm not worried that my bookmarks will be hacked or in some way used against me. My bookmarks are private and as secure as a pen-and-ink diary kept in a desk drawer. No, I just want to know where this might go. What can my database of bookmarks say about me right now, and what will they say in 40 years? How will I use them? What does it mean to have this breadcrumb trail digitised, databased, extensible, filtered, hyperlinked, synchronised, archived? Are my bookmarks worth anything, either personally or as raw data? How long will they live? Will I leave them to my children?