Google personalised search seems to being applied more aggressively, as will certainly be the case with other engines shortly. This led to a worrying situation tonight where a search for 'business type town' came up with adverts for 'completely unrelated business type town' because of the previous search.
I think this could be problematic when someone is refining their local searches or changing the type of business they are searching for.
As the matching in the above example is clearly wrong, assuming searches in a short space of time are closely related, I decided to do some more research.
I tried a variety of searches for differing heading/town combinations, some closely related and others wildly different. There was only one consistent factor, Google showed irrelevant adverts time and time again. Wrong business types were shown, or when I changed the town to somewhere quite far away there were adverts showing that had no connection to the area.
The nature of Local Search means both the business type and location have to be correct for an advert to be relevant, personalisation seems to put this relevance under threat.
Only time will tell if this will be a short-lived problem that gives us, eventually, better results or if Local Search is a step too far for personalisation (on general search engines) at the moment.