If you deserve it, like you really are doing something, then you can't complain, right? But when it's baseless and springs from mere paranoia, yay, it could get ugly.
I know of someone who was so paranoid about her boyfriend possibly exchanging e-mails and chatting with girls. The guy was friendly, but he was devoted to her he wouldn't do anything to betray her trust. The woman, wanting to have concrete evidence, bought software that records all the keystrokes you make.
How does it work? According to the guy's sibling, this program records every key you press on the keyboard, and then sends the report to the woman's email address. Initially she didn't have access to his email account. But thanks to the program, she was able to gain access to all his accounts--email, networking, and what-have-you.
The guy was exchanging emails with ex-girlfriends (yes, plural form,), but not with the purpose of rekindling the fire, or anything. It was just for friendship's sake(really!). But she was so jealous that she she couldn't help confronting him and accidentally mentioning the contents of the emails. That was how he realized she had somehow gained access to his email. He defended himself, by telling her matter-of-factly that really, the emails didn't mean anything. But she wouldn't believe him.
The guy asked his techie sibling to help him figure out how she could get all this information. (I can't tell you how he did it, suffice it is to say that he did find out that he had installed that program.) Sibling told brother about the program and as expected, it infuriated him.
Many other things happen which led to one thing--a bad break-up. And another kid with a broken home.