Now I’m assuming the reason this isn’t allowed is to prevent people from hosting their projects on the site. However, you could prevent this by setting the limit to 10kb. Since anything posted on these forums should be a code example, any swf that only has pure code should be less than this. 10kb is actually huge for pure code swfs. You could get away with 4, or even 2.
second, if possible.
This site got hacked several times due to Flash footers and attachments.
^It can be prevented now… but I guess better safe than sorry.