This is google analytics. It's a bit different than google directly taking the data and using it for google purposes (e.g. streetview cars gathering SSID information for location pinpointing). The data (afaik) is used only by the homebrew team instead of Google.
A more accurate summary would be "Brew is sending usage data to a google owned analytics service".
A more accurate summary would be "Brew is sending usage data to a google owned analytics service".