UPDATE (July 15, 2010): Twitter now has some official advice on this which you can read at this page.
Of particular relevance:
1. Your tweets aren’t recent: We only index tweets for about 6 days. If your most recent tweet is older than that, please tweet again and check.
2. Your account is private: Private or “protected” accounts do not appear in search. Learn more about protected accounts here.
3. Your account is new, or you recently changed your username: It can take a few days for new and updated accounts to be indexed by search.
4. Your email is bouncing: If you log in and see a big red warning when you’re at twitter.com that says your email address is having delivery issues, please take the steps to fix it! We want to show you in search, but we need you to fix your email first.
5. You are being filtered out of search due to a quality issue: In order to provide the best search experience for users, Twitter automatically filters search results for quality. This Search Quality help page has information why accounts are filtered from search
6. You are missing because of current resource constraints: Right now, some users may not be seeing their Tweets because of resource constraints. This is more likely affecting you if you’re a new user (with an account less than a couple of weeks old). Our search engineers are working on this known issue, and your Tweets should start showing up in search soon!
If none of this seems very helpful then you’ll need to file a support ticket at this page: http://bit.ly/twicket.
I’ve left my original article intact as below. Please note that it was written in June 2009.
For five days now, Twitter’s search has been broken. In fact, it’s actually been acting strangely for a lot longer than this – several weeks Â - but one particular aspect is relatively new. The problem is, this part has not been broken for everybody, so it hasn’t received as much attention as it probably should.
But it is broken for me. How? The ‘from:’ query in Twitter’s search feature, which lets you see all the posts from a given user, is showing that I last tweeted five days ago.
Now, we know that’s not true, as since that time I’ve submitted about twelve gazillion new tweets.
You can check this for yourself here. See what I mean? I laugh in the face of ‘realtime’.
This Is Just The Beginning
If it was just me being affected by this, I’d think myself either mad, or in the midst of some hideous conspiracy. But I’ve heard it from other people too, including my friend Zagrrl, who also, according to Twitter, hasn’t submitted anything in five days. This is also not true, as you can quickly gauge by looking at her timeline. It gets worse – some of my other contacts haven’t tweeted at all – actually, they have.
The reason why this matters is that many external clients depend on the from: search function to deliver replies to followers. As you may know, I use Seesmic Desktop, and within it I run a search for mentions of my username alongside my standard replies pane. Each time @Zagrrl has replied to me of late, it has not showed up in search. This is the case also for others in my network who have been impacted by this defect.
The catch, as I said above, is from my studies I see that few of the big names on Twitter have been impacted by this issue, or at least are unaware that they have, and this is why I think it is going largely unreported. The thing is, we all have, to a greater or lesser extent – from: seems to be completely ignoring my tweets for the past few days, but it’s ignoring ALL tweets from a week or more ago for everybody on the network. Even Oprah, who according to Twitter has tweeted only once.
It’s not just from:, either – a lot of Twitter’s search functionality is down. In fact, right now, you cannot search back further than 7-10 days (depending on the user) for anything on Twitter. As more than one wag has pointed out, it’s a good thing Twitter is pushing its ‘real-time search’, as right now that’s your only option.