This may sound a bit harsh, but all clans thinking this way are idiots. First: What do you declare as your land? Second: WHO do I ask? Third: There are many alliances consisting of more than one clan... WHO do I ask?
And if I ask every single clan who's territory I cross and wait for an answer I can stop strategus completely. Retarded...
1) Look at the diplomacy page, or click on the map, it tells you who is the lord of what fiefs, you should be able to decide where their land begins and ends (or what they are claiming).
2) You ask the people who control the territory.
3) You ask the faction who controls the territory.
In conclusion, these people aren't idiots. S&D is very important, and I'd rather have our faction buying and selling to use our S&D than to make 5 or 10% off of taxes (which also take money away from our traders and put them into the fief, which we don't necessarily want).