negative keywords maximum list
increase the number of negative keyword lists and/or the capacity of those lists. This accrues directly from both Google and Bing's emphasis on the use of Shopping Results in SERPs.
Shopping queries are based on a broad match and therefore produce an abundant amount of irrelevant searches, which requires the necessity of many, many... really too many exact match negatives.
This necessity could be easily overcome if both Bing and Google would allow for some limited use of Modified broad match. For instance - the exterior car covers industry - simply requiring that the search expression include the word "cover",would eliminate the need for the search terms that are matched against that DON'T include the word cover. We typically find CPAs at 4-10x of the desired CPA of search terms that don't include the word "cover". There is really no excuse for serving car cover ads on search expressions such as "Jeep Cherokees for sale" or even "jeep"... which happens often. Relevance, which is supposed to be the touchstone of paid search, seem to be lacking in Shopping.