There has only been 3 noteworthy eras of low level clanning that actually amounted to anything. I am not going to describe the days in early 05 where there were low level clans such as Final Ownage and Acid Projekt because they simply have no relevance to this discussion as it was far different back then.
The first was when Epidemic had a rivalry with The Dreaded (Undoubtably the most defining low level rivalry in the history of pure clans) in mid 2007, and other clans such as TGG, IR to some degree were also around in that era as "low level" clans or at least low to mid. The clans were pulling 50s with unparalleled organisation and leadership which made it very entertaining and pretty much set the standard for low level clanning in every other "era".
The second was the mid PCL time with clans such as Malice, Divinity, Sanctity, Absolution, Ascendency, Fatal Pures, and the various other clans that were around. This is probably the most filled with potential that a low level division has ever been and i personally thought this was one of the most entertaining times in which clans could have a fun filled rivalry safe in the knowledge that it was all for fun. This era was the first time low level clans full outted and pulled huge numbers, If i recall correctly Malice/Divinity each pulled around 80 to there full out after alot of mass recruiting from both clans, and most of the clans pulled at least 40 in there full outs.
The third and as I believe it the last "great" era of low level clanning was the end of PCL/Start of PvP era in which clans such as DP, Anonymous Assassins, Epidemic, Divinity, Violent Demise, Malice etc were around. This was the first time that low level clans were really transcending the boundary of divisions and having an impact on the rest of the pure world, with AA having impacts on the fights of MM to varying degrees, Epidemic smashing all competition and becoming #1 Clan in just under a year (Which shows that low level clans arn't pointless). Even when Malice/Divinity/Epidemic etc were truly low leveled in this era they were still pulling 50+'s with amazing organisation. Preps and big minis were commonplace, and overall it was very enjoyable.
Now, I really don't think you can argue that any other "era" has had any impact at all in terms of the bigger picture, now the low level clans are pulling 10 - 20 people which is hardly a defining moment when compared to low level clans of the past.
There will undoubtably be a new era of low level clanning (most likely when Me, Bob, Jibs, Plode, Ownage Milk and Maras0l open our new low level clan) but it just needs a clan to act like a figurehead and lead the way and set the standard, as clans have done in the past.