As someone who applied for a job that I didn't find out about until the last minute, when the application engine locked up and didn't submit my application I was quite pissed off. Unfortunately, it didn't notify me that it hadn't completed the application. A friend of mine was working at the company and asked me a couple of days later why I didn't apply, after he agreed to be a reference for me and really upsell me to the boss.

That would have been one hell of an addition to my resume, and it's far more likely that plain email would have worked. Of course, a recruiter wouldn't have got his cut...