At GoTo, only sites truly relevant for terms are allowed to bid on them. Moreover, search engines now spend significant resources in combating spam. Allowing paid links might greatly defuse the spamming situation, allowing them to concentrate their resources on improving search technology. Paid links certainly make more sense than trying to certify optimizers to follow rules that are already outdated. Even Bruemmer, who's leading the certification charge, likes the simpler idea of moving to paid links rather than certification.
Certification is within a certain paradigm that everyone is under right now.
What happened to Open Text is ancient history. An Internet month is like a year. Alternatively, perhaps some new developments such as link analysis or user measurements, as described in the earlier article, will make spam rules needless. Another idea is that new forms of trusted metadata may emerge, provided by a third party. Any of these might provide a real level playing field, and one that cannot be influenced.