how Shorten url will usefull for seo? example site goo.gl how many other site and how can we use this for right direction ?
It helps to visit your site and you can track your website visitors, where are they from, clicks etc.,
You have a long tail urls so sometime when ever you add so strictly some other timeline not add that urls so short urls is very useful for submission like a google, bit.ly and any other also...
yes this url shortening service can be useful in promoting, easily sharing links and it provides some more space for tweeting where we can add some more content in the same place.
The only thing that they can help you, is that people won't be able to see your FULL url (which sometimes shows that you are an affiliate (if you sell something)) and they will be more curious to see WHAT's inside the URL!