If it was my long tunnel, then it is fine (as long as you cleaned up after yourself). If you are the person who stole the ~200 Steel Ingots from me, then that was not proper etiquette. If you had asked I likely would have given most of it to you anyway though.
When I came into the server I looked in the chest right next to the spawn point and grabbed a couple of pickaxes, a shovel, a workbench, a smelter and a 64block of cobblestone.
Past that, I didn't take nothin' from nobody. Once I get my operations started I figured I would head back and drop some stuff off, seems like a good way to welcome newcomers.