It seems Yahoo will pick up new sites now and rank them for a few weeks then drop them. The way to keep your ranking is to build up your inbound links and have good onpage SEO.
I had a blogger blog shoot right to #1 within a few days, but the ranking dropped after a few months. Since then it bounces between #15 and #50. Yahoo seems to love new sites.
Google is too largely depended on and getting good in there is an awful lot of work and with the changes once you get in good will you honestly stay long?