I don't understand the mentality of people who think that when you hand them your phone to show them a picture, they are entitled to looking at other pictures you store on the device or worse, to see your contacts or what programs you have installed. Since when did I give permission to do anything beyond view that one picture?
One might say "well, you gave them your phone, therefore that's consent for them to peruse it" or "it's your fault! You handed it to them!". No. The latter blames the person giving their trust rather than puts the onus on the person who shouldn't have violated the trust in the first place. As for the former, let's say I'm in the kitchen with someone and I offer them a piece of fruit: would that be inviting them to take whatever they want from the cupboards? What if I let someone read one of my books; is that giving them carte blanche to use my bookshelf as their new personal library? In both instances, the answer is no and the same goes for my phone; I'm giving the person permission to look at that picture, and only that picture.
If someone wants to see my phone programs or other pictures, nine times out of ten I'm likely to say yes with the caveat that they keep out of the contacts and correspondence, mainly for the privacy of the people I talk to with the device. I have nothing offensive or overly personal in my pictures and the programs I've installed aren't something I keep secret; my objections stem from the person inferring that the one picture I allowed them to see gave them permission to look at more.
While writing this post I discovered this article, which goes into further detail about what I've covered here