Could you clarify it a little? If you have any information about filesize spoofing, I'd be very interested to hear your thoughts, since I've never heard of anything like that being done successfully.

The files you're seeing in the search results are not necessarily actual files. The filename, hash, size, metadata and everything else could be faked and the data is generated on the fly by a function while you're downloading it. This could be random data, nulls or something else that makes somehow sense.

*** I'm stopping at this point to tell you more ***

Keep in mind that not all spammers are interested in earning money with P2P. Certain organizations are trying to bug you until you give up P2P (search for T3 spammers and corrupt files)!