It seems to me Marriott doesn't actually have the software to "roll over" the nights as we would all understand it to mean... ie simply carry them forward to next year as a remaining credit from the previous. In this case the rollover is actually more beneficial than just doing that.

From info provided on this thread and others, I think Marriott has counted the rollover nights and credited them as if they were bonus nights awarded this year.

So what's the difference..? The difference is in the rolling calendar.

In ediemac1's case he was a silver with 30 nights for 2009 so he had 20 nights to rollover which then gets credited as 20 "bonus" nights. THEN kick in the rolling calendar which counts these 20 nights and those stayed in the last 52 weeks... which was, er 30... So 20+30 is 50 nights, one newly minted GOLD

Taking sghorwitz situation, 43 nights at silver lead to 33 nights credited to 2010, added to the 43 nights in the previous year is 76 nights, and a new PLT member on the rolling calendar