The ability to save and categorize a personal collection of bookmarks and share them with others. Users may also take bookmarks saved by others ... Book mark your site sertan bookmarking sites and book marking sites will get you good traffic.
It may not directly help with SEO but it helps get your pages noticed and hopefully if you have good content, people will link to you naturally, and that certainly helps with SEO.
Is it possible to get banned or blacklisted for hiring a submission company? Has anyone heard of this happening?
Choose the Social Bookmarking Sites with the most visitors and submit there all your URLs. Try to contribute instead of just spamming.