I actually have written a hub on Social Monkee it's called Build 25 Unique Backlinks A Day For Free.
I have my premium upgrade and in my hub I am placing others referral link (not mine) who have joined up from that hub. Out of five people who have taken my offer, three have been upgraded already. The remaining two just need a few more and they have their free upgrade.
As to Social Monkee it bookmarks to one hundred sites all on separate ip classes. The idea is that you get one hundred backlinks that are all dofollow. In time these sites will only get stronger.
Is it any good? Well if you have a new hubpage that you want spidered then yes it is. If you want 100 backlinks then it is also good. If you have a blog or article you want to get some links to, then once again this is good.
A free upgrade, scheduled bookmarking, rss feeds of the urls and you can ping the lot. Now when I say free, you gotta love that.