Photo sharing fits the bill just right. Facebook has shown you can also make money off it.
Ecommerce is always a great market, but it's too vague because it's just commerce through a new medium. I'd prefer and love to read blog posts discussing specific ideas. Take that as reader feedback :-P
Did you see this Mixergy interview with the founder of Gemvara? http://mixergy.com/matt-lauzon-gemvara-interview/
It is one of the most innovative ideas I've come across recently, and apparently executed very well too.
To be honest I didn't want to name specific markets as I didn't want to create too much interest in areas where friends of mine are working. I didnt want to add attention and make it more crowded. :)
"It is all about execution. Even if you have a great idea - 5 other people will have it at the same time."
Just quoting a blog post...
Great point. A very good write-up on that is http://jasonlbaptiste.com/featured-articles/build-what-had-p....
Maybe I will write a post on how to identify a great market, as that is a pretty big topic.
For what it's worth, I'd love to see you write that.
"Great market" /= "hot market"
Great market to my mind is a market that has a lot of users who will use your product (and better yet, you can make money off of them using your product). Maybe I will write a post on how to identify a great market, as that is a pretty big topic. But one example is often markets where user behavior is fundamentally shifting, or where there is a sudden change (e.g. adoption of truly smart phones) leading to opportunity.
I think certain areas in ecommerce are a good example today of changes in user behavior and business model leading to high growth companies (Gilt Group was just the beginning, and some really cool companies are getting started today around fashion/women's goods online).