I am also having this problem. I find myself having to periodically reboot to prevent the install from occurring.
I definitely, DEFINITELY have not clicked "Install" because the last 2 times I have upgraded to 8.1 I eventually wound up with a corrupted install and had to reimage my machine. The 1st time I wasn't sure what caused the problem, but after the 2nd time I noticed that it only happened after I updated to 8.1.
I've kept 8 installed for the last 7 or 8 months and I haven't had a single problem. Given the amount of work it takes me to update my machine (my base hardware configuration is Vista, then I have to use my Win 8 update, then I have to reinstall all of my applications)... I absolutely guarantee I did not "accidentally" click on anything.
I find forcing an install to be intolerable given that it essentially forces me to reimage and lose data. Similarly I find that representatives placing the blame on the community to be a terrible decision that is not customer-focused. If you don't know if your software is doing that I'd much rather you own that ignorance rather than deflect the blame.