Flickr App for iOS now support Hashtags.
What’s New in Version 2.11.820
- Hashtags! Add a hashtag in your photo’s title or description, tap on the hashtag and instantly see all photos with that hashtag.
- #FlickrFriday: Add #FlickrFriday to your photo and instantly participate in Flickr’s weekly photo challenge. Details and the weekly theme here: http://www.flickr.com/groups/flickrfriday/
- Bug fixes
Everyone loves hashtags! Even Facebook is reportedly working to support hashtags.