Server Select Screen
As far as I know, the servers are ordered top-to-bottom based on increasing server load, with the heaviest loaded servers (Freedom and Virtue usually) at the bottom. The top slot was reserved for the server on which you were most recently active. Any further re-ordering (like what you are talking about, based on amount of activity per server) would probably require some more complicated algorithms, since every player would have a different order to their server list. It is probably easier to have a uniform way of ordering the servers, to avoid problems. After all, the more complicated something gets, the number of possible problems increases. I cannot say for sure how difficult it would be to do what you are talking about, but the above is my guess as to why something like this has not already been implemented.
@Winter. Because I'm Winter. Period.

I am a blaster first, and an alt-oholic second.

I was thinking that they could have them ordered like character slots are ordered; in the character select screen, the player chooses the character order, which is stored on the local file.
Topher Wade lvl 50 Claws/Regen
The Crimson Heroes Society SG
Chaos Faction VG
Official Naturalized Citizen of Justice since 2007
I don't know if this has been brought up before, but I was unable to find it, so here's my suggestion:
Start tracking the server that is chosen at the server select screen, so that we can see the servers in order of most-selected. That way, when I decide to jump on my one toon from Protector, I don't have to look around and find Justice all over again. This is mildly annoying for me, and I can imagine it being much more annoying to someone who plays on separate servers often.
Topher Wade lvl 50 Claws/Regen
The Crimson Heroes Society SG
Chaos Faction VG
Official Naturalized Citizen of Justice since 2007