New Adwords Feature - Intersecting Queries: No thanks, we’d like to opt out!

I have a better understanding now of what’s happening when sponsored links appear to be unrelated to the current search query and a hangover from the previous search query.
I blogged about it a couple of weeks ago showing an example where a search for wedding celebrants followed by a second search for string quartets resulted in a mix of ads for both celebrants and string quartets on the same page. Simon from the Found Agency pointed me to their blog post on the same thing where they have screenshots showing combined results for car insurance and child care.

Google’s explanation quoted on Search Engine Land is:

look at the user’s previous query and see how well it intersects with the current query

My initial interpretation was that this is based on some kind of semantic or topic matching. In other words an assessment of how relevant the second query is to the first query. I lost faith in the relevance argument when most of the examples I came across were for two queries that appeared to be completely unrelated - like the car insurance and child care example.

However it appears that the intersection is based purely on the combination of the actual words in the two queries. Mike Churchill has a detailed explanation but basically if all the words in a keyword phrase are present in the combination of search query one and search query two, then the ad will show on the second search if it didn’t for the first. For example, someone has the keyword phrase “large orange widgets” in their campaign. A search for large widgets will not show the ad but if this is immediately followed by a search for orange cars then the ad for large orange widgets should appear in the second set of search results as the two queries combined contain all the words.

The end result is untargeted and irrelevant ads. Not good! Even worse, as Mike points out, there isn’t a great deal you can do about it without adding a lot of complexity to the campaign management. There’s quite a lot of discussion happening about adwords “features” that are unwanted and detrimental to advertisers. This thread about expanded broad match on high rankings is one example. Maybe we’ll start to see some changes if Google starts to listen to their bigger advertisers or if enough people start recommending wholesale changes like avoiding broad match keywords.