Micallef, the links he is building are being built. Xrumer and SB can build hundreds of thousands of links if you want them to.
However the reason why only a few are showing is because they are not being indexed, especially profile links. If gorang is not going to any extra methods to actually INDEX these links at all, then he may as well not build them, in my opinion.
And the worst thing about social bookmarks is, specifically Pligg, is that most of the time you have to 'vote up' the story using another account in order to transfer your story from upcoming (nofollow) to published (d0-f o llow). This pisses me off greatly as you can bookmark the shit out of your site but only see it buried among thousands of pages of upcoming bullshit and zero chance of being indexed, and even then it will be no follow.
My own experiment on 'excessive' backlinking went like this: I manually made 200 useful, relevant comments on high PR 3-7 blog pages (not domains, actual page PR) on a new site and my site went up to page 1 (no 5) for a couple weeks. Then it went down into the oblivion (still indexed) and I haven't seen it since. This was 4 months ago. It's still indexed and everything but not ranking for shit. In yahoo and bing on page one.