yeah, you just shouldnt set it to a value that would allow file sizes bigger than you expect or desire.
like for example, very few websites would need to set the max to 2gb, because files of such size are prob not desireable anyway.
you also need to consider what happends if someone were to upload a 500mb file, and you need to process, move it etc...if a few people are uploading a file that big at the same time, your out of memory pretty quick, and everything comes to a crawl.
and again, like said above, this is really only a major issue if your on a shared server, or your website is really busy.
its not fair to let 1 user on a shared server consume gobs of memory, slowing 50+ other websites down dramatically.
if your on a dedicated server, then you just need to make an educated guess of how often large files are uploaded, and what the chance of 2 or more user uploading big files at the same time are, and set a value that would not consume more system memory than your willing to allocate.
i beleive apache has its own max request size values, if i remember right i think its like 16mb, so you may need to adjust that as well.
