Google gives them out (literally) to sites that are authoratitive in their niches and have a LOT of quality inbound links. In other words, a site like the American Medical Association would get them since they're an authority on the topic, but Joe Sixpack's blog about medical news and health information would not. (Yes, I really dumbed the answer down - I'm not home and I'm really not in a mood to discuss SEO right now due to a family member having just gotten home from the hospital after a near one week stay there for cardiac and respiratory problems.)
Bah, sitelinks are nothing. Check this out, a search engine http://www.google.com/search?hl=en&q=php&btnG=Google+Search
Your site must be massive in order to get these and usually they are in the no.1 position. I don't think they are very important and would actually prefer a normal listing than site links.
I think that is attracting users to do more clicks on your site. If you want the same you should add much more strong inbound links.
well good traffic and if people keep on searching for some thing repeatedly from a particular site google automatically makes them site links and we have to wait for that to happen ?
there are ways of eliminating some of your sitelinks once you get them (say you only want 3 of them for example)
Hi, Google give this information about a site if it is a highly viwed forums or if it is a social media. google comes to know about this. so that way google set this format.