Each piece of custom content makes the download a bit bigger. Small items, like cosmetics and eyecolors, aren't too bad, but custom skintones are the worst offenders. They can make a file that should be no bigger than 20-50 KB upward of four MB. That may not be a big deal to some people, but I happen to be on a dial-up connection around here, and I don't want to download something just for, say, the bathing suit and wait an extra who-knows-how long for the stupid skin tone, which I'll probably never use anyway.

You don't see these as often as the first item I mentioned, and my description is an exaggeration, but you get the idea. It annoys the heck out of me when people try to tell everyone how gorgeous/talented/perfect their Sim is. In fact, it makes me want to hurl.