bookmarking on google,yahoo,digg etc

bookmarking on google,yahoo,digg etc is banifecial ?
or what banifit of it ?
for search engines ?
or only for us ?

The goal is to create backlinks.

99% of the time, they won't do anything for you. 1% of the time, you may get a ton of traffic from one well placed link.

And, it's also very niche specific too. ie, if you're not a tech site, digg likely won't do anything for you. But if you have the newest info about an iphone, you can get 2342343423423 hits in an hour from them.

it mean book marking is use less just time wasting ?

Bookmarked url gets more attention by SEs. I observed once i bookmarked my forum to some dozen of bookmarks. I got alot of traffic. I recommend you prefer DO FOLLOW bookmarks. I can give you one example folkd.com it's high pr and dofollow social boookmarking site.