I also do not normally post but just in case it helps here's what's been going on for one of my sites.
- site ranked in top 10 of G for almost 8 years for many terms and one particularly popular generic term.
- 15th April dissapeared from rankings (still indexed, pr etc)
- 19th June came back again
- 28th June (to-date) nowhere to be found
- two competitors with similar content still ranking
- have not carried out any link building for a year or so