I am sure you might have come across several posts on alternative to adsense. I hope you never need to try them. Let me tell you this: "Nothing can ever be a remote alternative to Google AdSense.
I agree there are alternatives to AdSense but poor ones. Nothing can ever replace Google AdSense. Till date, I have never read a positive testimonial on any of these alternatives to AdSense.
Long before I read about upcoming ads similar to Google ads by Yahoo and MSN. About them too, there is hardly any mention in blogs and forums.
Ah yes, I almost forgot. Are you aware that the Google has formulated new procedures for approving AdSense application from publishers? It involves two stage verification by the AdSense team.
Read all about this blog post by Max Cohen, Product Manager