How intensive are we talking about here?
If you're burning two or three villages per day (which is a very high rate and almost impossible to maintain without your player party contributing) then you'll cut them off from about 60-70% of their recruits for 10-15 days, bump the price of food up a few notches in their towns and maybe cause a clan on the brink to start losing money. It isn't worth it as a one-and-done deal though.
If you keep that up over 30-40 days though, repeatedly burning out any village that recovers, it has an effect. The prosperous towns will start to starve because they rely on the +10 and +15 food bonuses from their villages, even after the villages recover. If those towns remain prosperous, the price of food will get pretty high because it is being imported by caravans at a mark-up. The garrisons will start to clear out due to starvation and being rummaged through for troops by lords who can't recruit from the villages.
If you keep it up over 84 days (a complete in-game year), village notables will start to disappear faster and faster due to the power loss they take with every raid. A lot of their towns will start to take snowballing prosperity hits because at low hearths, village parties are small enough to get killed off by smaller groups of bandits, which causes the "Has Problems with X Bandits" quest to pop more often. And that quest is absolutely devastating in terms of its "Bound Settlement Issues" penalty. You can legitimately cause towns to go -10 prosperity per day if all their villages have the quest pop.
It takes forever though and in the end the effect isn't any worse than just taking settlements from them, forcing them to fight over it. The starvation effects caused by raiding are nice but you can do that and add in the penalties of being besieged to really kick the pain into high gear.
What he said.
The relation hit is also bad for you since you won't recruit from notables.
AI has different recruitment than the player,they already have a set relation with notables and they usually won't lose anymore.
This is also proven by the fact that AI can recruit from villages that have been raided,which reminds me I should report this bug.
So AI is raiding more consistently without a penalty in relation,if it's a penalty is small since I haven't seen AI gain new enemies or friends.
If you're gonna attack a village,make sure you attack it constantly so that the notables recycle and you get new relation,dunno if they carry their previous notables relations,I need confirmation on this.So don't take my word on this.
If you want to raid,you could let an AI allied party or neutral start the raid and join in,you won't get any relation loss with the notables or their faction owning.
But you also won't gain a lot from the raid compared if you were to do it solo.
My suggestion is to raid villages with horses,first check what they have for trade and then make up your mind.
If they have Aserai Horses,Warhorses or Cows since these are more valuable.
