DV25 compression is about 5:1 (25Mbps) , so a little under 5 mins per GB or about 13GB per hour of footage. It is a constant bitrate which is why DVDs can take up less space for similar quality (they can use less than 5:1 for relatively static scenes for example)
Remember the colour information is compressed with NTSC DV25 down to 4:1:1 (from 4:4:4 or 4:2:2) so yes DV throws away a lot of information.
Remember even huffyuv uses compression, (although lossless), uncompressed 4:4:4 NTSC video comes in at over 30 Megabytes per second!

There is an (outdated but interesting) comparison of DV vs Hi8 here: http://www.adamwilt.com/DV-Hi8.html