Welcome to the Q&A Forum

Oh yeah, forgot about that. But considering you are providing you DDoS protection, CDN, optimization, etc, their fee is still very low for a pro account.

I agree. As a link building method, social bookmarking is bad. As a method to drive buzz and get exposure and links for awesome content, Reddit and similar tools can be great. Reddit, StumbleUpon, and similar tools are not really social bookmarking sites, either.