As for compression goes, it can possible be a boon. It can also bite hard when it doesn't work correctly, I lost a disk full of data once because of that.
Not data compression, that's not what I mean. I used the "compression" expression to simplify the explanantion, but I guess I'll have to explain seeing as you've come to the wrong conclusion.
Data compression on computer disk or media files (mp3, DivX etc) just looks for patterns in data, and then keeps 1 copy of the pattern instead of every copy. Then a map of where the copies occur must be made to re-assemble the original data. If the map gets damaged, there goes your data, as there's no way to re-assemble without the map. That's what happened to your hard drive, the map got corrupted.
All I mean when I'm talking about compressing transactions is encoding the exact same information in less space, but without depending on a map charting the repetitions in the data. When the shrinking of the data doesn't need a map, the risk you're referring to is no longer an issue.
There are two types of compression, lossy compression and non-lossy compression. Lossy compression is tended to be used on sound and video files, it reduces the size of the file, but it also reduces quality. In many cases people do not notice the loss of quality. Hard drive compression is non-lossy, that is you will get the same file back when it is uncompressed (e.g. zip file). If wck lost data due to disk compression, then it is due to the file or hard drive getting corrupt.
There are some compression techniques that are intensive to compress, but unintensive to uncompress. This type of compression would be good in a crypto propagation system, since nodes could store and pass on the compressed data and validate it rather quickly. The downside is that the miner takes time to compress it (and runs the risk of being orphaned in a block creation race).
Then of course there is more efficient transaction encoding. This is not actually compression.