There have been reports in the Google Places Help forum and on Mike's blog that TripAdvisor reviews have gone missing from Google Maps, Google Place Pages.
One business owner said:
we have in the last week lost all of our tripadvisor reviews from our google place page...
Mike received a statement from Google saying it is a bug and the reviews will return. Google told him:
We're aware of a technical issue in which TripAdvisor reviews are sometimes not appearing in results for Google Places, and our team is working to resolve the matter.
So if you lost reviews, this may be why.
Forum discussion at Google Places Help.

Comments:
Sam Daams
12/08/2010 11:30 pm
Interestingly, Tripadvisor is saying they blocked Google Places from including their reviews (not sure how): http://www.tnooz.com/2010/12/08/news/google-places-blocked-from-using-tripadvisor-reviews/
Phil in West France
12/09/2010 08:57 am
As Sam says, the story from TripAdvisor and reported by Tnooz is very different. Not a technical issue but a spat meaning TA has blocked access. If they can't agree, why believe them?
Andy Kuiper - SEO Analyst
12/09/2010 06:50 pm
Mixed messages on this as some are reporting TA pulled the reviews... wait and see I guess.
Dan_43
12/10/2010 09:13 am
Lets hope they stay off, Trip Advisor is disgraceful, guess Trip Advisor dont want to be associated with the true reviews
hotelthirtynyc
04/06/2011 04:39 pm
This has ntohing to do with anything you may or may not have completed. Google may be having issues indexing tripadvisor for some reason, though I have not heard anything over the wire about it. Hotel Thirty-Thirty