Consider RAID to mitigate the impact of a possible crash. You can acquire two 2 TB drives for < $200 and with either a SATA RAID board or a full enclosure for $149 you would have a robust solution for < $300.
It does protect you against the most common scenario of your primary PC tossing a hard drive head for a 1-time expense. It does not, however, give you offsite backup in case of fire/flood/EMP/lightning strike.
If you want disaster recovery, that's when you're talking mozy/carbonite (carbonite - unlimited? really? for some reason, reminds me of the Simpsons episode where Homer got kicked out of the all-you-can-eat-buffet). They're great, but I don't see how that give-away-disk-space model will not lead to future price increases and you are trusting them to not break/lose your data. Depends on your level of trust I guess.