Reddit is within the non-intrusive ads policy of Adblock Plus. So Reddit Ads arent blocked by default.
Here’s how you can disable all Ads on Reddit Using Adblock Plus chrome extension:
1. Click AdBlock Plus extension in your browser
2. Click Filter Preferences
3. Select Custom Filters tab
4. Click Add Filter group button
5. Give any name for the new filter group
6. Click the actions button of the new filter group
7. Click Show/Hide filter button
8. Click Add filter button the right pane
9. Type static.adzerk.net and click the Close button
Enjoy Ad-free Reddit!