One other issue with backups is whether incremental or "everything".
A lot of people do incremental, never realising that a restore will require ALL the media which the previous versions are on to be OK - unlikely. For most situations, backing up the complete data set (or the whole HD) is the only meaningful method.
And doing that over the internet is a problem if using ADSL. You can't backup gigabytes over ADSL.
It does suprise me that tape is still around, after all the talk of terabyte storage on molecules, accessed using lasers, etc. This has been just around the corner for about 20 years. I guess tape is cheap, big enough, and the need to break up the media for (a) the hierarchy and (b) offsite storage is what has kept tape in business.
Absolutely central to the situation is the fact that you cannot (in most cases) systematically verify that the data you are backing up right now is undamaged. That's why keeping old backups is essential.
At work, we backup the accounting software to another PC every day, to a zipfile, and these zipfiles end up on tape each weekend. So we get a daily backup without any tape involved - the only risk during that week is a fire which would take out everything since the w/e. Doing a daily backup would be a problem because the tapes would be used so heavily that many would fail.....