We are all obsessed with sites like Twitter, Facebook and Linkedin at the moment but rewind a few years to when the term Web 2.0 first popped up and a whole host of different sites were the hot young startups destined for great things.

It’s amazing what a couple of years do though because as we can see below, some of the biggest sites from the “Web 2.0 generation” are either on a massive decline, facing huge competition or about to be closed down. There’s a good lesson here to highlight; how the hype cycle around websites and services can come and go and what was once lauded and destined for great things can within a couple of years shut down and be abandoned…

Delicious

One of the most popular and useful sites of the Web 2.0 era, this massively practical bookmarking tool was used by many people to keep track of content that they found online. Yahoo bought the site at its peak but users have started to drop off (the graph below might not be reflective as many people use browser plugins etc) and just this week there was speculation that Yahoo are pretty much going to be killing off the site much to the amazement of some of the loyal user base who use it on a daily basis. Fortunately that isn’t the case but the company is looking to sell.

Digg

Possibly the highest profile of all the casualties given it’s rise to fame, the high valuations it received and the online celebrity of its founder Kevin Rose. The traffic had started to stagnate and fall last year but the downturn really accelerated this year when the returning Rose tried to introduce a whole host of new features to try and compete with Facebook and Twitter but those changes backfired spectacularly by alienating the loyal community and the site is shipping users as fast as they once gained them.

Flickr

I wouldn’t say Flickr is in chance of dying nor has it’d downturn been as marked as the other sites on the list but there is no doubt that it is under pressure from a whole host of new photo sharing sites. Flickr is still massively popular but the rise of Twitter and sharing sites like Twitpic, Yfrog and newer apps like Instagram are certainly making people share photos in a whole new way.

Myspace

It’s amazing to think that just over a year ago Myspace were still competing directly with Facebook as one of the world’s biggest social networks but now the decline is so significant that Myspace has had to redesign their entire site and allow you to use Facebook connect to make the site more social. The site has been re-positioned to focus on content but it’ll never be the force it once was and you shouldn’t be surprised if you hear it’s closing down sometime next year.

Bebo

Not as massive around the entire world as it was in Europe and some other markets but people did think the site had enough potential for AOL to pay $850 million for it. Since then the users have pretty much left it and AOL were trying to give it away for free to anybody who would take it. The latest valuation was somewhere around the $20 million mark and you can expect Bebo to fizzle out completely pretty soon I reckon.

What Does All This mean?

It means that you shouldn’t hedge all your bets when building up social media profiles or community within a site. Even though you are getting great results or find a site massively useful at the moment doesn’t mean that in a couple of years it will be the same site. Trends come and go faster than ever on the Internet and sites that you one couldn’t live without are obsolete within a couple of years. I just cringe at some of the money brands poured in to the likes of Bebo to try and promote their products and grow an audience and what are they left with now that Bebo is in a digital cemetery? There are probably sites out there that we all use and love on a daily basis which in a couple of years will be closing their doors and it’s important to just be mindful of that.

Read next: Internet in the Classroom [Video from 1993]