About a month ago, Adwords announced to us that it was changing the behaviour of exact and phrase match to match close variants, including misspellings, singular/plural forms, stemmings, accents and abbreviations.
The changes, due sometime in mid-May, have been sold as a positive change for users, creating a behaviour similar to that already employed for organic search. Google hopes advertisers too will like the changes, as it will help them avoid missing out on relevant traffic.
The reaction amongst advertisers has been mixed however, with some suggesting that the changes serve only to increase revenue by reducing advertiser control.
Google has offered an opt out in the interface for advertisers who don't wish to take advantage of the changes.
Our own analysis indicates that this may not have yet taken place (search query reports are usually a couple of days behind), meaning that if you haven't considered the impact of these changes yet, it could be your last chance.