When processing an atom feed, if the link element follows an image, textinput, summary, tagline, subtitle, logo or info attribute within an entry, that link will be attributed to the feed URL instead of the entry. Atom feeds which do not have a link attribute before those other elements (most, including many atom feed samples around the web), will have the same link URL for every entry as a result.
The aggregator module is virtually unusable for atom feeds unless attributes within the entry are ordered to accommodate.
Parses correctly
<title>This is fine</title>
<link href="http://example.org/" />
<summary>The link appears before the summary.</summary>Parses incorrectly
<title>We have a problem</title>
<summary>The summary appears before the link, and so we have a problem</summary>
<link href="http://example.org/" />