You can wirelessly stream some types of video, audio, and image files from your ThunderBolt to your TV using DLNA as long as everything is concurrently connected in some way to the same WiFi router. Even if the TV itself is not DLNA capable and is not directly connected to your network, you can send the streaming media signal through another DLNA capable wireless device such as a Sony PS3 game console that is hooked up to the TV and connected to your network.
You will also need to install an app on your ThunderBolt to get this to work smoothly. I think the "Twonky" app works best for this purpose and handles the most video formats. Twonky is a free download. HTC also sells a DLNA adapter that hooks up to the TV through HDMI, but that adapter costs more than $100, and the phone still communicates with it wirelessly even though the adapter uses a wired connection to the TV. You do not need that expensive hardware adapter if you already have a PS3 hooked up to your TV and connected to your wireless network. Unfortunately, there is no way to stream media from the ThunderBolt to your TV using a direct wired connection.
The DLNA connection works as advertised, but JPEG images are sent rather slowly, so it is time consuming to browse through them. The stronger your WiFi signal, the faster the performance should be. The video and audio files may take a little time to load, but they play fine once they get started. A DLNA connection is better than nothing, but it is much less satisfactory than a direct HDMI wired connection would have been. DLNA also does not allow you to mirror everything that is happening on your ThunderBolt like an HDMI connection would. DLNA only allows you to stream media files.
Video files you have taken with the ThunderBolt's internal cameras should play fine over a DLNA connection, and I have also been able to play some other video files, including DVD movies I converted to avi format and copied to the phone's micro SD memory card, but not all video formats will play using DLNA. It is very unlikely you could stream a Netflix video to your TV using DLNA because you cannot store the Netflix video file on your phone, so you would have no file to point to. I have not tried to stream a rented or purchased Blockbuster movie or Google video yet that has a file stored on the phone. I would be quite surprised if DLNA would work to stream such proprietary and digital rights protected types of video files to a TV, but it might be worth a try if you don't mind spending a little money for the download. DroidTV downloads video files to your phone, but these video files are hidden. I have not been able to find the files on the phone so far to attempt to stream them to my TV over a DLNA connection. Good luck!