What about the increase of the block size, then ?
Even if 512o per transaction is small, it might represent a significative amount since all has to be stored in the block chain.
I will tell You what have i just done.
I clicked "quote", copied the message and pasted it in a text file.
Then, i have truncated the file to 512 bytes, and EDIT:
GZIPPED it. It now takes 329 bytes.
Next, i have bzipped it. Now it takes 288 bytes.
Of course, there is no need for such a long message. Let's try 384 bytes. I used lorem ipsum generator from here:
http://lipsum.com/Results:
-rw-r--r-- 1 user user 384 2010-10-23 19:09 ipsum.txt (uncompressed)
-rw-r--r-- 1 user user 274 2010-10-23 19:08 ipsum.txt.bz2 (bzip2)
-rw-r--r-- 1 user user 268 2010-10-23 19:10 ipsum.txt.gz (gzip)
I think that maximum ~260-280 bytes per transaction is not bad.