I bought cheap advertisement space from something like +50 different blogs. Niches: Blogging recources, online marketing, making money online. Average price for ad slot was 2-8 ecs. Campaign should go on next 1-5 days.
I didn't really spent time studying how good investments individual blogs where, my strategy is to create 'shotgun spreaded' visibility for my own blog. Sinces Entrecard ecs are virtual currency, this time I didn't use real money, just my virtual capital on entrecard.com.
I will report results during following days. :)