Its opening potential backdoor in your system.
It is a widely used program that even some business's use. I would not describe it as a backdoor.... as you know it's allowing you to connect to your machine. So treat account as such that is used to log in. Honestly check it out - https://www.teamviewer.com/en/download/current-version/
Would I put it on a machine being used as a wallet? No.. you should treat them with extra security. But would I install it on a PC to connect to miners when away from home, or to connect to PC's that mine with GPUs sure.
I'm not making it up you can see how popular it is just by searching. Here is some of it's security - http://www.teamviewer.com/en/security/ . Before jumping to thinking it is a backdoor look at Velkro's trust to see what kinda person your getting info on security from - https://bitcointalk.org/index.php?action=trust;u=303026
Teamviewer is a very good and professional tool to work on it, it really helped me a lot as i am a computer engineer so many times i have solved minor problems of my customers through Teamviewer software as i was not able to attend them personally so through teamviewer i have solved their problem and more then 2 yrs i am using and never faced any problem