i think most of the webmaster is aware of the webmaster tools provided by google ... in your opinion do you think that sitemap is useful or not ? if so .. what if you have a website which you update on a daily basis ... and it's kind of a pain in the arse if you have to update yourself sitemap every other day ... what if you don't update your sitemap .. will google be able to crawl your new pages which isn't included in the sitemap ?
Your answer is NO What do you think if I'm not using webmaster tool bar then my sites doesn't crawled by google. there were so many sites which are not using google site map and there are doing well. Yes I accept that if you are using this tool then you should update your xml site map it can gives you more benefit for your new pages for indexing by google
if your site is having complex link structure and its vast enough then you must sitemap and update at frequent intervals. See there is no gain without pain.If you are getting benefits from SE's then you must follow some protocols of it..
Adding sitemap will have two advantages,it will result in faster crawl of your website and user if not able to find any information, can go to sitemap and find it.
I will say yes and no for the sitemap. For my idea if we use the tools which do the absolute link and create a beautiful links like joomla / Mambo (+plugs in) which generate nice absolute links. The sitemap may or may not much require and necessary. If you use some program like dreamweaver that generate relative links inside your site. I think to get a better PR on many bots, we need sitemap. I also believe if we only update the page without add any new page should not require to update the sitemap.
Why wouldn't you use an XML sitemap if a search engine recommends it? Would that be rather a silly thing to do? Sitemaps are great because it lays out a map of all your web pages to search engines, which the 3 major search engines currently follow; the XML sitemap format. No, it doesn't increase SERPs or get you indexed faster but creates a map they can use to find new web pages or older web pages they have yet to crawl.