This is a tough question. Ads connected to ad networks can potentially deliver malware, but I try to think about it in terms of trade-offs — risks and benefits. Knowing the potential risks and benefits, you can make an informed choice about whether to whitelist a site. I personally avoid sites that require me to turn off adblockers, but that’s just my preference. If the benefits of accessing a site are really important to you, whitelisting is a legitimate choice as well.