When using progressive profiling as part of your lead nurturing efforts, I've found capturing one high value piece of information at a time works best. For example, if you are going to offer a case study, video or whitepaper for download, only ask for either email or social media log-in credentials and company name. Then when a prospect responds to the next call to action in the nurturing series, ask for an additional piece of information such as industry or pain point and deliver content based upon information gathered from previous interactions. This not only creates a personalized experience but it keeps the tone conversational.
In addition, you should be incorporating your lead scoring criteria into this process so subsequent interactions will boost up your prospects lead score! With any relationship, it's best built over time and there's no better way to do this then with progressive profiling.
As a next step, why not try out progressive profiling using Eloqua's new Cloud Component How to do Progressive Profiling in E10 Using the Cloud Component