Here's an excerpt from the earnings conference call about the concern that Walmart will switch to private label spices. I don't know for sure if it's accurate, but others have posted here that MKC is the supplier for Walmart's private label spices, so I guess the worst case scenerio would be that MKC would see their margins cut if all Walmart business became private label.
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"Now as we move into Q&A, I’d like to address the most frequent question that we’ve been getting from investors for the past year concerning the spice category in Wal-Mart. In a limited number of stores, Wal-Mart will be testing a category solution which expands private label to core [A&C] spices with no duplication by McCormick or other regional brands for these items.

In a similar number of stores, Wal-Mart will test a total McCormick solution with no private label and a third set of stores will test a set primarily with McCormick and very limited private label. We wouldn’t normally discuss this level of detail concerning any of our customers, but there’s been so much attention on this that we want to provide as much clarity as possible to our investors.

We will limit our comments on this test, but I’d like to add that we expect no significant impact to our financial results during the tests. We welcome this opportunity to optimize our category with Wal-Mart as we do with all of our customers.

Spices and seasonings are one of the most profitable categories for our customers in grocery. McCormick has been the leader in this category for decades, driving growth, innovation, superior merchandising, and bringing consumers aisle with advertising."