If you're referring simply to the screen shot capability, say on an iPhone, then a Snapchat user is informed when you take a screencap using that method. I think that once upon a time the user was not notified but Snapchat must have updated; I confess I am an avid user of the medium and I am notified when my friends take screencaps using the typical methods. I honestly don't really know why it matters if the person knows you took a screenshot or not. You're still taking a screenshot of something that was (probably) not intended to be screenshot. And if you're using Snapchat you should be aware that other people CAN easily screenshot what you're sending and hopefully trust that those you send pictures to won't.
Meh. Not really. Although at first it seems the only purpose of Snapchat is to send nude or illegal pictures, I use it frequently and 99% of the time not to that purpose. If you like sending captioned pictures that are forced to be live - you can't send screenshots or pictures you've preciously taken - it can be a fun way to stay in touch with people. Honestly, most of the pictures I send and receive on Snapchat are selfies with captions. For instance I woke up this morning and my friend had sent me a Snapchat of her looking beat, and captioned it "16 hours of sleep and I still feel like death." I sent her one of me making a face back captioned "I'm awake." I think some people use Snapchat like texting. My #1 Snapchat "best friend" (they rank your top three) is my cousin who lives in TN. Instead of texting we snapchat to each other. Yes I have used Snapchat for more...dubious purposes but it is very rarely, and it's partially because I know you can take screenshots. And also I just try not to document anything that's going to get me in potential trouble with my employer, even if (theoretically) the picture disappears after a few seconds. Point is, people don't use snapchat just to send pictures they don't trust to regular texting. It has become it's own thing. Is my apostrophe right?
To your question -- no. Possessive. "It's become its own thing" would've been fine though. Anyway, I guess. I don't use Snapchat and I personally can't understand a mindset where I would want to send a picture of my face to someone with a caption. All down to personality type. But I think a lot of people (especially middle school and high school kids, who I would hazard a guess are the primary userbase?) liked the knowledge that whatever you said was gone, and not just because it was a nude picture. There are lots of reasons not to want conversations shared at that age. But again I've never used it and don't honestly know too many people that do.
I think you're right. Today was a groggy morning. Edit: Although "it's" can also be a contraction of "It has" which is what was throwing me off. In the same sentence you see I spell out "it has" because I originally wrote the sentence with two apostrophes and got kind of confused as to which one was right.