A vegetarian friend was kind enough to set me straight about iceberg lettuce - it has certain characteristics that make it the perfect lettuce to shred and top dishes with (never buy it shredded, they use some kind of vile preservative that hits my gut hard). There are salads that benefit from the extra crunch a little iceberg adds to other varieties of lettuce. For a long time I didn't buy it, but now I have iceberg and romaine both handy in the crisper.