IP agreements are the least of your worries. They don't matter that much and are really really hard to enforce. Basically it matters if you steal some kind of trade secret of a lot of existing clients/contacts.
Not having enough time to properly do your startup should be your main concern.
this is dangerous advice -- regardless of whether or not enforcement on these agreements is likely or possible, you will spook investors/acquirers if you don't do your due diligence in this area and don't have the necessary documents to prove ownership of your IP.
Aren't you the guy that emailed me? Sorry I wasn't able to meet up with you at startup school.
I still don't think its that dangerous of advice. Sure, if somebody is working in a similar industry, doing actual work on the start up in the work place, then that'd be a problem. Businesses often do have large portfolios of IP, many having not much to do with their business, but I don't think somebody is going to have a problem working on something totally different, at home, on their own machines, on their own time.
right -- but if your employment docs say, for example, that your employer owns all IP you create including stuff you do on your own time and out of the office (yes, a draconian clause, but not that uncommon!), you can be in big trouble if your startup takes off and your former employer is legally entitled to (i.e. you don't own) the IP you created -- either your employer can try to lay claim to what you've built or your investors/acquirer will find out during the due diligence process and not move forward as a result.
that said, i'm not a lawyer, and i'm sure others can provide related nightmare stories -- but everything i've heard indicates it's really better to not screw around, and to have a paper trail indicating that you own your IP.
Not having enough time to properly do your startup should be your main concern.