Okay this is my own theory of the Google dance & Maybe a recommendation?!
Okay I think why some sites leave google (this is for google quality sites, not sites doing spam etc) I think google keeps a cached file or something that tells on average how many backlinks a site gets so if the amount your getting fluctuates highly from the average it bumps you out until further analysis is done..remember we are in a viral world now, so something from your site may have gone viral and thats why your getting the links, google cant tell this is manual linking because as long as the links are quality how would the computer be able to tell . Ie..why sites who have established that page 1 rank rarely dances because to get to one you must of started from somewhere and have some sort of consistency..For example my site had 35 backlinks over 4 years lol (i know) and in the last 3 weeks I got like 600).. My theory is obviously google must have multiple service centers in different locations that gather info on sites like backlinking & change in content etc. (I noticed this also because before i started backlinking I changed the meta description, and when it showed up on page 2 it had the new description and when it showed up on page 8 it had the old description) So I think what happens is when your doing your backlinking if your doing alot the service centers have all different information..For example if you build 30 backlinks using west coast ips..then you build 90 on the east, those servers will have different counts of backlinks. I think why it disappears is because Google is trying to figure out where to put you and they need all relevant info. How can Google put you ahead of someone when it doesnt have all the info and know where you should be. I think when the info is all gathered up in one place then the serps show. Same thing happened when I ordered a service from here...the backlinks were pinged over a week, so my serps would jump from page 8 to 3 and all over the place. Now with your service since you ping all the links in a short period all the service centers in the different areas where your ips are located have different info. So I disappeared completely off the ranks..once the info is updated google will know in comparison to the other pages where i should be.. So I was asking if you have the option of pinging the links ie...20 a day..it may be more time consuming but I think it may stop the dancing.