I've got one. It's currently running raspbmc (tried openelec, didn't like it) and it's stuck behind the TV on XMBC duties. Currently planning on buying a few more to go around the house.
Also re private mailservers, I've never found it hard, but then I run mailservers for a living, so I guess doing what I already know helps things out.
Yeah, that's just based on what i've read.
But I think you would need quite some gear and effort to get it running spam free.
No gear at all, just a bit of reading and applying knowledge. I wouldn't run one on a rpi tho. You want a vm/vps for that. I get mine from Bytemark (
www.bytemark.co.uk). Plonk debian on it and follow the tutorial at ispmail -
http://workaround.org/ispmail/squeeze and you'll be up and running. If you don't have any domains, use
www.gandi.net as a domain registrar. I started running my mailserver in about 2003 (pre my currnet linux job) and it helped in getting my current job as a Linux sysadmin. The anti spam stuff isn't hard at all. If you use postfix, then using postscreen, postgrey and spamassasin plus a couple of RBLs will sort you out for anti-spam. If you're geeky enough to come on a site like Geekhack, then you're probably able to run your own mailserver if you want.
re write cycles, I really wouldn't worry about it, most cards have 1,000,000 write cycles, which means in real terms you have to be reading, writing and erasing data for about 3 years solid before you're likely to kill a card. If you want to find out which app is polling the system when it's running, you just need to get a program that tells you which program is writing to which and you'll know. But I really don't think it's worth worrying about. SDHC cards are so cheap these days, replacing them every 3 years is not a biggie (and that's assuming constant usage).
As for why it uses an SD card? I think it's cause they're small and don't take up much space.
