What you talking about? Take the three large guilds which managed to achieve a level ~80 or higher: two of those guilds existed already in June 2010 (when the system was released). It took them 9 months to get there. The third guild shows up first in July 2010. They achieved their current guild level after 8 months. Now I have not researched all the guilds of level 65+, but would not be surprised if the picture is similar (ie: it took them in excess of 6 months to get to their level).
Meanwhile there is a small guild who first showed early February 2011. They managed to achieve level 83 by mid March. You cannot possibly deduct from a small guild managing to achieve a level higher in 6 weeks than large guilds managed after 8-9 months, small guilds don't have enough an advantage.
In other words, given the data we have things may look distributed evenly in level but small guilds outperformed large guilds in level as much as 5! times as fast. Now, don't get me wrong - I am not trying to bash those guilds. They were probably very disciplined and dedicated in getting to where they are. Well played. More power to them. I am merely contesting they are somehow at a disadvantage or don't get enough a bonus.
The thing that does both me about the system that at the high levels it is too heavily slanted towards managing your decay. You want to exceed a level (which appears to be roughly the low 80s) you just cannot afford to allow people in your guild who do not produce regularly. It's not that it takes longer or is getting harder, but I am afraid it is just not doable. You have player(s) who for whatever reason cannot invest hours of play time every day, you will hit a hard cap on how high your guild can go; not within months, not even within decades. You suffer decay for all those accounts every day, but might only get contributions every four days a week. It's simple math really, there comes a point these accounts propel decay so high the more active members of the guild no longer can support the additional weight.
Maybe that's the intention and the highest guild levels are supposed to be reserved for guilds consisting almost exclusively of very active members, but that does still not mean I have to like it.