I have no idea what other people are going to say but I have been doing just that for 5 - 7 posts per day with no issues at all to about 15 bookmarking sites. It has helped my serp on my 2 year old site targeting a mega competitive niche.
Your social bookmarking account should not have only bookmarks from only a single domain. Add few random friends, random urls and continue doing upto 10 submissions per day. This way you ll stay under the radar imo.
hmm thats great. i assume people will say not to do it everday b/c it needs variance. idk tho. How long have u been doing it? bookmarking the same post to the same site once or multiple times?