[7Figures2Commas]

The devil is in the details and it's worth reading the following text closely:

Any provision in an employment agreement which provides that an employee shall assign, or offer to assign, any of his or her rights in an invention to his or her employer shall not apply to an invention that the employee developed entirely on his or her own time without using the employer's equipment, supplies, facilities, or trade secret information except for those inventions that either:

(1) Relate at the time of conception or reduction to practice of the invention to the employer's business, or actual or demonstrably anticipated research or development of the employer; or

(2) Result from any work performed by the employee for the employer.

2870 provides a lot of protection to employees who are very careful but a lot of employees are not careful enough to meet the criteria above.

[defen]

#1 is the real killer. If you work for the Googles / Apples / Facebooks of the world, basically anything involving computers is going to fall under "actual or demonstrably anticipated research or development of the employer"