... is that people who adopted it don't understand really how things work. The moment one installs a backdoor into a program, that can be found and accessed by anyone. And usually the people looking for those are either working for security companies (case in which it isn't that much of a problem, provided those people's ethics are intact) or not - and it's the latter that carries some issues with it.
I can understand the concern for security, however this exposes everybody, not only people with malicious intent, and it can have effects that ripple beyond getting law enforcement new tools. It can put everybody's data at risk and this means everybody, from large corporations who are using backdoored software to individuals trying to protect their naughty (or not) private pictures.
I suppose it all boils down to stopping usage of the cloud, storing everything locally with drawer HD and/or optical medium backups, middle fingering iCloud, Dropbox, Google Drive, OneDrive and so on. Losing convenience over gaining safety and security is one way of dealing with the whole issue.
As for browsing histories and what not, I don't really think people who wish to do harm are googling incriminating stuff or accessing suspect websites, so it's all looking rather pointless. Then again, people give up their data rather easily e.g. to Google for convenience, so the issue lies with educating people. I fear though that when it will become apparent to everybody, it will be too late. People don't realise it now, in the 11th hour, albeit there are strong warnings out there - https://en.wikipedia.org/wiki/...