It's come up as an answer for two questions:
Here is the main page: A Week in the Life of a Browser - Version 2: Aggregated Data Samples
But the download links for the 3 data files is dead. For example:
https://testpilot.mozillalabs.com/testcases/a-week-life-2/witl_small.tar.gz
The relevant HTML source for the page can be found in this GitHub repo
<table class="callout">
<tr>
<td><span class="headers">Filename</span>
</td>
<td><span class="headers">Download Size</span>
</td>
<td><span class="headers">Num. of Tables</span>
</td>
<td><span class="headers">Num. of Users</span>
</td>
<td><span class="headers">Description</span>
</td>
</tr>
<tr>
<td><a href="witl.db.gz">witl.db.gz</a>
</td>
<td>1.1 GB</td>
<td>3</td>
<td>About 27,000</td>
<td>Gzipped SQL dump of all three tables</td>
</tr>
<tr>
<td><a href="witl_large.tar.gz">witl_large.tar.gz</a>
</td>
<td>469 MB</td>
<td>3</td>
<td>About 27,000</td>
<td>Gzipped Tar archive of three CSV files, one for each table</td>
</tr>
<tr>
<td><a href="witl_small.tar.gz">witl_small.tar.gz</a>
</td>
<td>7.4 MB</td>
<td>3</td>
<td>About 27,000, 387 w/ event data</td>
<td>Gzipped Tar archive of three CSV files, one for each table</td>
</tr>
</table>
In this case, the links to the download files point to the same folder, which is empty otherwise.
Who can find these data sets? (so we can properly host them)
One hint: find this guy and see if he still has a copy.