Comcast has begun injecting ads into webpages accessed by users using one of its 3.5 million public Wi-Fi hotspots. With this action, Comcast joins the list of businesses (e.g. airports) that provide Wi-Fi service with ads.
Another potential solution is to use a VPN, which encrypts all the traffic between you and the VPN provider instead of between you and the website.
The risk of security vulnerabilities being introduced by ad injections is just one more item on the list of things you have to worry about when using a public Wi-Fi hotspot. Other dangers include shoulder surfing (not just people looking over your shoulder at your keyboard and screen, but surveillance cameras), people having physical access to your computer when you use the bathroom, and the interception of unencrypted traffic using freely available tools such as Firesheep (see Steve Gibson’s post on how hotspot providers can easily mitigate this threat), the need to install a firewall to protect from threats from other users on the hotspot, accidentally connecting to decoy hotspots with similar names that eavesdrop on your data, and more!
With all these risks, you might want to ask yourself whether it’s really so critical that you check your e-mail right now at the nearby hotspot. It may be better to wait until you’re back home.