How to grow a service that is popular but never took off?
lacker: Keep making it better. If you're out of ideas, ask some of your users what they use it for, what if anything annoys them about it, what more they would want. Take everything with a grain of salt but maybe it'll be helpful.It might be handy on your homepage if you linked to some popular examples of people using this. That will get them some more traffic and make your top users more likely to use it in the future.Add a send-to-friends feature after someone has made a map.If some of the maps are public, how about having a combined map that shows all notes live as anyone using your product posts to it. That will give people a sense of what they can do with it.Add a video showing people what they can do with it.Try to white-hat SEO your site a bit for searches like [make your own map]. Do you get a lot of traffic from Google? What are those searches for? Looking at that might give you some ideas for what they are looking for.Make widgets that make it easy to embed these map in peoples' Myspace or Facebook pages.Make a mailing list for people interested in your product. Or a forum. Start creating some community; talking to your users will help you understand what they want or need.Start a blog where you talk about and link to cool uses of your product.Make a twitter mashup where anyone who tweets with a lat & long gets their message posted on the myguestmap. (Maybe you have to ask people to add a #mygm tag too.)Just some thoughts. Good luck!