Bad impact of memory_limit set to -1 ?

Hi all, I fighting with SoapServer to be able to upload large file base64 encoded. Every so often I get memory exhausted error messages and memory_get_usage() tells me that my script starts with more than 250MB allocated (for a soap request of 85MB!). I'm wondering if I would let memory_limit unbound (-1) to avoid those issues but I don't know what would be the consequences (esp. on apaches processes, total allocated memory, etc). Any advice ? Thanks, Manuel