Please note that what you read from this point is basically all true. I am sure that 99% of it is the truth*
I am translating what I read from korean blogs, and plus what people around me have told me in the past. 
This is serious stuff so please don’t be alarmed/scared. I was shocked when I heard it too, so it’s okay.
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Saesang incidents:
1. When Infinite used to live in their old dorm ( the very small one from “sasame player”(?) ) after “Be Mine” got popular, a saesang entered when they were sleeping and took some clothings of theirs.
2. When they moved to the dorm featured in “A Birth of a Family” (?), a saesang fan pretended to be a resident in the apartment and entered the elevator together with Myungsoo/L. Myungsoo had a instinct feeling that this girl was a saesang, so when the floor for Myungsoo arrived, he gave her his usual fierce stare and cocked his head a bit. When she saw that, I guess she felt a bit scared and ended up not following him. But as he was going into the house, she yelled “The fans should know of this kind of behavior toward your fans!” and ran off.
3. Now, Infinite moved to a new apartment, and recently, some saesangs again took their clothing and took pictures while they were sleeping. Also, it is reported that they do this when Infinite leaves the house vacant. After that happening in their new house, no matter how best they tried to keep the saesangs away, Myungsoo and Sunggyu cried.
4. When they went to Japan, some saesang fans in Japan entered the hotel room and stole some articles of clothing/items. They are in Japan. They are tired. They should be able to sleep peacefully and get some rest without all this stress.
5. Infinite had to apologize multiple times to the neighbors near their dorm because the saesang fans were being very loud. That is the main reason why they have to keep moving; the saesang fans leave trash and other things in front of the dorm,so neighbors end up filing complaints.
6. A saesang fan came too Woohyun’s brother, Boohyun’s restaurant and was being roudy, loud, disrespectful. Boohyun couldn’t possibly yell at the girl, because it would disturb other costumers, so he ended up posting an apology on the online site of his restaurant. 
7. All during the day, saesangs are always outside, trying to take a picture of something they are doing. Saesangs usually stay hidden, that is why normal fans cannot spot them all the time. Most of them secretly take a picture of them sleeping.
8. Sungjong and Myungsoo were exiting a building, and suddenly Sungjong was stampeded by the fans while Myungsoo was in front. Myungsoo looked back, and came back to get Sungjong. Myungsoo grabbed Sungjong’s hand and pulled him out of the crowd saying “I told you to follow me well! You wanna die?” (with a very serious face).
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This is by far, all I know… There is more, and I will post if I find out more about it.
If you are reading this, this may be a huge shock to you, because you did not know how much Infinite is suffering from all these saesang fans. I know I almost cried when I read them.
But this is the hard-cold truth about being a well-known celebrity in Korea. Being a celebrity isn’t all what you see on Television. 
I’m not saying all fandoms go through the same things, but this is Infinite’s as far as I know.
Be free to spread this around to prevent any more of these kind of fans.
If you think about it, Infinite is just a bunch of boys in their 20’s that should be allowed some freedom in what they do. They are essentially like all of us; being a idol group shouldn’t have them scared of fans, and worried of their every action.
This is very saddening to me, and I hope all of you guys keep this in heart. 
(Source: jjangddongwoo)

Note from me:

This is not only for Infinite but other idol groups that may have this experience happening to them.

I know that they are just fans and so but you guys need to know that people in general need their personal space. Imagine that they weren't idols, you wouldn't even know who they were because the world is so big. But because their name is out all over this does not give you the ability to go through someones stuff and take things because you 'adore' 'love' them. What you take could be something so precious for them. What you do could hurt them so bad.

They can break once, twice but once shattered they can just want everything to end. End can mean anything, their life, their job, their career. Everything and once it has happened you'll regret it.

Please just leave your idols in peace. They want to be in their own homes knowing that it's safe just like you and I want to feel safe and secure in our own homes.

Thank-you for reading this and I hope you try and spread the word around in your own blogs and so.