Do you mean less requirements for a blogger or for an advertiser? I believe PPP's key requirements for a blog are 90 days old and 20+ posts during that span. PPP offers run-of-network and segmented opportunities for maximum flexibility/ROI, but the advertisers decide those requirements on an opp-by-opp basis.
I suppose Blogsvertise are the easiest to register with as a blogger with but instead of logging in and checking for opportunities they email you offers - not very regularly at that. The trick is to register with several of these companies instead of relying on just one.
yes, reg with many agencies and keep your blog updated. Here are some other paid blog posting services