Reputation is a fascinating topic. It's important in tasks such as spam-blocking, but it's also a matter of knowing who and what to trust. For example, when someone recommends something in a web forum, or emails you a 'hot stock tip', how do you rate that?

I was reminded recently how much of a problem this can be by a posting on Techworld's forum, asking for information about a specific piece of software. My curiosity was piqued not by the software, but by the poster and the way the post was written.

So I first did a local search, then fired up Google - and sure enough, the poster was a shill. That's someone who pretends to be a member of the audience, but is actually working with a conman to make the rest of the audience think the conman is genuine.

Then it happened again, and this time it turned out that the second shill had posted similar queries and recommendations on at least a dozen other web forums, all relating to two products from the same company.

That got me thinking. The value of the Internet as a source of expert advice has been debated ever since it was invented. In the early days, only academics and techies used it, so it was pretty much a given that if you found information or advice online, it came from a reliable source.

Online communities such as CompuServe also tended to be fairly reliable. Getting connected wasn't trivial - it cost you money for a start - and they tended to attract groups with shared interests, both amateur and professional.

In fact I still belong to a very long-standing online conferencing service called Cix. When I have a question I need answered, it's the first place I turn to - but its user numbers are declining, and the web is to blame. Cix charges subscriptions, and there's just too many websites out there offering forums and chat in return for nothing more than viewing a few ads.

It was the advent of the web and of consumer services such as AOL that changed it all. The sad joke was that "90 percent of what's on the web is rubbish, the difficulty is knowing which 90 percent."

Sloppy tabloid newspaper hacks, idiots forwarding chain-letters, and even a few police officers who ought to know better - all have been caught out by hoaxes which they believed "because it was on the Internet".

And all those web forums, designed for experts to share knowledge, got cluttered up with lusers too dim to come up with a decent Google search string to answer their own questions.

Thankfully, the web has got a lot better in the last few years, as companies have switched to using it as their main publication method, as decent search tools have allowed us to filter out more of the rubbish, and of course with the arrival of professional publishing outfits such as Techworld.

But every once in a while, I find myself reminded just how many people still undervalue reputation. They might be getting rubbish, but it's free rubbish, so that's OK!

Technology can help discover reputation, but it's time-consuming - for a start, you need to know how to use a search engine properly and then filter the results.

Could that process be automated? It's a nice - but also slightly scary - thought.