The Next Web points to a Tweet from developer Shahruz Shaukat noting that the desktop version of iTunes is currently experiencing an interesting glitch in which searching for "podcast" or "podcasts" in the U.S. iTunes Store yields only a single app result: Apple's own Podcasts app. Clicking through to "See all" under both iPhone and iPad apps similarly displays only Apple's app.
Default results showing only Apple's Podcasts app
The issue is clearly a glitch, as the behavior is not consistent across international stores and even within the U.S. store, where the issue appears in the default "All Results" display but not when results are filtered to show only apps. The issue is also not present in searches performed in the App Store application on iOS.
Filtering results to show only apps displays full set of results
Apple has yet to fix the issue, which was noticed by Shaukat over 18 hours ago.