This will need to be tested and confirmed but I think I've come up with an issue between the anti-splog plugin and the Post Indexer plugin.
Today I had 4 blogs marked as spam by anti-splog, they were all blogs that were supposed to ignored but weren't (that's a problem for another thread that involves BBPress). ANyhow, when I unspammed the blogs to make things right, they now longer showed up in the recent global posts widget that use on my front page and which gets its data from Post Indexer. I had to rebuild the index for blogs to get them to show up again.
Is this the default behavior of Post Indexer? Is it is, what can be done to improve the handling of it. Every now and then a legitimate blog gets marked as spam, having to rebuild the index for as part of the process of getting it unmarked gets to be time-consuming (there is also the time period that goes by when the blogger starts to complaining wondering where their posts are - and I have to tell them, be patient, it takes time).
Not a huge deal, but if it can be confirmed, perhaps something that can be looked into for a future update to make these two plugins more compatible.