I've become convinced the ultimate benefit of the Internet is and will always be the ability to connect people. Lots of people know this already. You can see evidence of it by the rapid pace of new Social Networking web sites being made. But I'm not interested in these billions of MySpace rip-offs.
There have always been people-matching sites on the web. Dating and Friend-finding sites (connecting individuals to meet in real life) and sites for finding jobs (connecting employers with employees) are some of the most common examples. We can also see people connecting through the uses of forums, blogs, online groups and other communities. But I think there is a lot of potential for specialized sites that solve a very specific problem for a potentially large group of people.
Take a look at BookMooch. This is a new site which lets people trade used books. No money is exchanged. Instead you get points for mailing books to people, and you can use those points to get books mailed to you. It is a perfect example of the potential of connecting people. It's not just connecting me to you so that we can chat about our shared interests. It's about connecting anyone who wants to trade books, and allowing the most complex of trades to happen very easily. "I'll give this book to her, and she'll give that other book to him, then he'll give some book to you, and finally you give this book to me."
Web professionals should check out Programmer Meet Designer. It's a place for finding freelancing partners who can help out each other in any number of ways, from a few hours on a single project to a permanent professional partnership. Most notably, it's geared to a specific yet large problem of matching programmers and designers, and it solves the problem well.
The possibilities are rather endless, and I think the room for competition or co-existence between these sites are quite large. For example, there are a large number of job searching sites which co-exist in harmony. As I outlined earlier this week, there are job searching sites which specialize in jobs for web professionals. There are also dating sites which specialize in every conceivable niche. People can use more than one of these sites at a time, and many do.
If you're trying to come up with a new web business, try to find a way to connect people who can benefit from each other. These sites will always be in demand, simply because everybody benefits.