I'm not one to usually abuse one move or specific combo repeatedly in what we used to call 'being cheap' back in the day, but I will admit to doing it once while using MODOK. I was playing in a player match, and at one part of the fight, I kept spamming his psionic beam special with Medium attack, and even though it's a relatively slow start-up, my opponent just couldn't get out of it. I don't know if he was stupid and didn't try to block it or what, but he kept getting hit by it as he was standing up like at least 10 times in a row before I stopped doing it because I felt bad.
He also had his mic in, so I heard him yelling over my speakers since I didn't have mine on. He was cursing in frustration and after the match, I got a nice little voice message telling me I was a *@!$&@!#* *@#!&@! **$!&%!@% !@#!%!^ and that he would hack my account and rape me. Or something very similar - I didn't listen carefully to all the cursing and threats.

So I can't say for sure at this point, but I'm thinking I should have taken the threat a bit more seriously, although I don't know what I really could have done at the time.
After getting that rage message from the guy, the past 2 days I got a few random phone calls from various institutions like ITT Technical College and University of Phoenix, apparently calling me because I requested information from their websites. ITT told me they got my request through the internet, and UoP actually told me my correct email address and said that is what showed on their record for the request.
I go and check my email and indeed I do have random messages for a few different websites saying I signed up for email lists and whatnot. A few online education information sites, and military.com, some with my real name and some with this random name that is not me. I go and unsubscribe from them all, and realized that this may be due to that idiot guy who threatened to hack my account.
My guess is somehow he discovered what email address I use for my Windows Live ID for my gamertag. How he did this, I don't know. I'm pretty sure I don't relate my email address to my gamertag in any public way anywhere on the net, and the only way the two are related at all is through the Windows Live ID.
But anyhow, I'm sort of paranoid now as to how much of my information this guy found on me and to what extent he'll take this. So far it's just been the random phone calls and emails, so at least he didn't hack my gamertag in the traditional sense as in finding out how to log in as me and do stuff. But, I'm just worried that this isn't the end of it.
According to the customer support rep when I called Xbox, the only things I can do are to change my Windows Live ID, change my gamertag, file a complaint through the console feedback system, and block him.
I changed my Windows Live ID but I don't know how much that will help since it seems like actual profile information is tied to the gamertag, not the WLID. I think I'll change my gamertag just in case, but I'm kind of pissed that I have to pay the 800 points just to feel slightly safer against further attacks. Although the guy that maybe hacked me already knows my info, so I don't know how much that will help either.
One weird thing about this is that some of the random emails had a strange name, totally not me, while maybe one or two had my real name, even though they were all done around the same time frame. So while there may or may not be more than one cause to this whole strange scenario, I'm inclined to believe it was all due to this hacker guy. It's just too random to not be related.
I've never been victim to such an attack before, and it really sort of shattered my sense of security online. I'm not stupid and generally practice safe habits online, but somehow this guy was able to do all this just based on knowing my gamertag. And maybe having this one username spread across various outlets isn't such a great idea as I thought it would be.
So moral of the story: be careful how you play online. Even though it's just a player match, some people take it way too seriously and aren't well-adjusted enough to handle a loss, even if it's a frustrating one.