Amit, by observing your blog's permalink structure and that of many other top blogs around the net, I found that the two most popular permalink structures are:-
example.com/%category%/%post-title%/ and example.com/%post-title%/
Labnol uses, labnol.org/%category%/%post-title%/%post-id%/
But, WordPress documentation (http://codex.wordpress.org/Permalinks) strongly recommends not to use text fields (like %category%) in the starting of permalink structure for performance reasons instead it suggests to use a numeric field in the beginning (like %post-id%).
For performance reasons, it is not a good idea to start your permalink structure with the category, tag, author, or postname fields. The reason is that these are text fields, and using them at the beginning of your permalink structure it takes more time for WordPress to distinguish your Post URLs from Page URLs (which always use the text "page slug" as the URL), and to compensate, WordPress stores a lot of extra information in its database (so much that sites with lots of Pages have experienced difficulties). So, it is best to start your permalink structure with a numeric field, such as the year or post ID.
Similar advice comes from this article (http://www.weberz.com/blog/2009/06/seo-experts-give-wrong-advice-wordpress-permalinksthis article). There is an interesting debate in the comments of this article.
On the other side, many people use post-id in their permalink just for sake of inclusion in Google news, but some articles say that Google news no longer needs the numeric identifier in the urls (http://www.blogstorm.co.uk/google-news-no-longer-requires-stupid-numbers-in-the-url/).
So, if one is already planning to use post-id in his permalinks, is not it better to start permalink structure with post-id?. It makes URLs unique and database friendly.
I think you must had taken into consideration this factor while deciding the permalink structure for DI.
Waiting for your opinion about this. Whether to use post-id in the starting or at the end or do not use it at all?