No, it is not common. I've never heard of anything so overreaching. It would indeed deter any other company from hiring you, startup or otherwise. And I think it tells you all you need to know about the company you're considering working for.

Since you're using a throwaway account anyway, would you mind telling us whose agreement this is?

Thanks. Based on your feedback, I plan to turn down the offer unless the agreement is changed.

Regarding the identity of the company: I am concerned about embarrassing the company publicly. I can email it to you directly. It is possible that this is not a typical agreement at the company. I would be working in a group where IP is of greater than usual concern.

EDIT: Mailed to you at ycombinator.com with my account name in the body.

PG is right that it's not common. The problem with this provision is that it would require you to divulge the confidential information/trade secrets of third parties (e.g., your new employer, your startup, etc.) after your employment with the Company ends. And in the software industry, 6 months is a long time. The year-long obligation to disclose patent applications is troubling as well, especially since patent applications are treated as non-public/confidential information by the US Patent & Trademark Office until they are either published (which is 18 months after filing), or issued (if they are not published by special request).

It seems to me that this Company has this unusual provision probably because it got burned by a former employee who left the Company, joined a competitor, and filed a patent application for an invention that was conceived while he was at the Company. In such situations, the Company should bring an action to contest the ownership of the patent application rather than asking its employees at the outset to execute an agreement to violate the confidentiality agreement of any future employer.

This kind of thing is negotiable. Don't be too harsh --- they are just trying to protect themselves, and went about it in a rather evil way. But good people can accidentally make mistakes that turn out to be evil.

If you explain to them your concerns, they will probably change the agreement for you. My friend had similar concerns about the company he was applying to, but after they talked about it the company cut the offending part from his agreement. I know my friend would've regretted not taking the job, if he knew what he was missing out on. It's apparently a fun place to work.

For big companies sadly that's pretty normal from my experience, I've had to sign a similar agreement a couple times. That's how ebay is suing google for google wallet. What you can do (what I do) is give a very broad prior art base (they can't claim any work you have previously worked on). When I was younger since I already worked on a huge range of projects they can't claim I originated an idea while working with them. Sometimes they are even willing to narrow the agreement, depending on the level of your position.

Learned about it when I got screwed a few times during college for a couple inventions. At the time I thought the bonus was a fortune (5 figures), but looking back they screwed me royally.

You need to consult a good IP lawyer on this issue and have her/him do the negotiation for you. If you really want the job you can probably negotiate the limitation to a specified subject area and require them to sign mutual non-disclosure agreements for each and every disclosed bit of IP. Remember to declare all future hobby projects to keep them in your control.

It would be nice if you were to publish the name and embarrass them in public.

I'm pretty sure that you can't throw away your Section 2870 rights. But then again, I would consider it less than honest to sign an agreement with the intention to challenge it if it were enforced. Also, not legal advice.

I would read that as a short lived slavery contract and never sign such a thing. My freedom to act on an idea I have at any time is much too important for me to give up.