I love mashups, and I seek out and devour them with nearly the same fervour with which I read webcomics. The two artforms are quite similar, actually, in that they both conform quite solidly to Sturgeon's Law - there's a whole lot of crap out there, and you have to know how to sift to find the good stuff.
I like listening to mashups for three main reasons: a) they introduce me to artists and genres I ordinarily might ignore, b) I find listening to multiple overlapping melodies and harmonies mentally stimulating, and c) they introduce hyperlinks between melodies in my mind, so if I hear a song later, I can almost-sorta hear the other song in behind it.
If you're not familiar with the mashup artform, or have only heard bad ones, I recommend you head over to Youtube and search for names like DJ Earworm, DJ Magnet, DJ Lobsterdust, DJ Zebra, or Norwegian Recycling.
(Tuesday morning, INT: MH's apartment, kitty room, EB has her phone out.)
ringtone (faint): When the pimp's in the crib, ma, cram a scorpion up your urethra!
EB: I mentioned that back in college, I went through a bad breakup, right?
EB: Well, near the end of that whole process, I was up at an inadvisable hour, under the influence of inadvisable substances, and I made an inadvisable phone call.
ringtone (faint): When the pigs try to get at you, shove a red hot poker through your goddamn gut!
EB: I wound up leaving a series of increasingly loud and hysterical death threats on his answering machine. Rather than retaliate directly, he got the sound file uploaded to some message board.
EB: Someone created a Flash animation of some blond bimbo caricature to go with it, and voila: I was a teenage Internet meme.
ringtone (faint): When a nigga get an attitude, shit directly into your living brain!
EB: It's kind of embarrassing, I don't really talk about it much.
JH: Okay... that doesn't explain who that other guy talking is.
MH: The ringtone is actually "Dump it like it's hot: Answering Machine Bitch versus Snoop Dogg".
ringtone (getting louder as they get closer): I got pustules on my arm and I'm pouring boiling acid and I roll the best shit 'cause I got it going on.
EB: Standard mashup nomenclature. I do not currently have beef with the West Coast Crips.