I agree - so often when clients switch to an online application service (which is absolutely a step in the right direction), they miss the opportunity to simplify the process. Why make it hard for candidates to apply? I really can't see how it would help the client to have the CV filename in a specific format - they must have a horrendous back-end system ...

If you're going online - great - and take this opportunity to streamline the process, make it easier for the candidate and yourself. Take advice from your technology vendor as they will have implemented many systems and will be in a good position to advise you on how best to 'cut the fat' as Thomas put it. If you're not sure they are giving you the best advice, find someone else!

I don't know what Adam's experience is in recruitment or in being involved in implementing e-recruitment systems, but my experience says exactly the opposite.
Do not follow or even ask your technology vendor for this type of recommendation - ask your most experienced recruiter.
Too often the technology advisor is mostly interested in implementing the system with as little change as possible & seeks to implement a singlrestandard version to keep costs lower.

I bet that's how most of these really awful "registration" processes get implemented. Screen after screen of required information before you are "permitted" to apply for the job. I've sat in on meetings where everyone but the recruiter ( that's me ) has said " well if they are too stupid or too lazy to fill out these 5 ( count them - 5 ) screens to register - we don't want them!