The use of a "trial week" says to me that the company in question sucks at being able to accurately assess candidates, and is taking the cheap and easy (for them) way out. I know that other companies are capable of doing a good job of interviewing someone in a day or two, why can't these people?
I can't think of any circumstance under which I'd entertain an offer on these terms. I don't think any of the people I've worked with and can recommend would, either. This company is probably losing good people up front; folks who have been around, have experience, and can go elsewhere with less hassle, and so who don't bother to send in a resume.
All told: Meh. I'm not impressed.
The more I think about it, the more I become convinced that this practice can open you up to a tortious interference lawsuit from a former employer of one of your hires.
Keep in mind that, even in the context of non-compete, California isn't the be-all-and-end-all of the subject. It is the state where the prior employment took place that matters. (Usually, choice of law questions can get complicated.)
Exhibit B
CALIFORNIA LABOR CODE 2870 NOTICE:
California Labor Code Section 2870 provides as follows: 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. To the extent a provision in an employment agreement purports to require an employee to assign an invention otherwise excluded from being required to be assigned under California Labor Code Section2870(a), the provision is against the public policy of this state and is unenforceable.
If you were to 'trial' an employee who had signed a copyright assignment agreement with his current employer in a state where such agreements are enforceable, the prior employer would have a colorable argument that it owned any code written during that week.* If the employee had signed an agreement containing an "anti-moonlighting" provision, again in a state where such provisions are enforceable, the prior employer would have a cause of action against the employee for breach of contract and possibly against your company for tortious interference with a contract.
As I say in the sibling comment, I really think you should talk to your lawyer about this, particularly since the policy is now been subject to a fair amount of publicity that a disgruntled ex-employer might reasonably come across. Although I don't like your hiring policy, I have nothing against your company and would hate to read in a few months that you are bogged down in litigation.
*Federal courts have exclusive jurisdiction over copyright actions, but will apply substantive state law in interpreting and applying contracts. Which state's laws can be complicated, but the most likely one is where the employment took place.
Locality aside, non-compete isn't what would get you here.
For most companies, they likely have specific policy in place - that you agree to around taking outside work while still employed by them. It might be they allow it, in which case it's fine. More typical is that you need to get some level of approval for work that doesn't conflict. In some cases they ban it outright, though I suspect the latter isn't particularly enforceable.
Certainly I've been in situations where I've picked up non-conflicting side contracts, and my employer has turned the other cheek because the approval process was tedious. However, that will vary significantly by company, and - legality aside - IMO they would've been within their rights to call me to task for it, because I knowingly agreed to their terms on the matter.
"Employers of salaried employees generally don't need cause to fire employees"
That's only so much handwaving. Yes, they generally can fire you for any reason or none at all. On the other hand, they typically won't. Unless you give them cause by taking an action contrary to the actual terms of employment you agree to. Then they certainly will do so.
I'm not disputing the risk of doing a temp-to-perm project for a prospective new employer. But the operators of these programs would probably retort by saying that they're the last step before confirming that you're giving notice anyways.
I'd view it overall as less of an issue if there were numbers better than 2/3rds (I believe I saw posted elsewhere) proceeding to the offer phase. To me that represents a huge risk: a 33% chance that I'll have done this contract work, lost vacation time, and jeopardized my current employer relationship.
If the number is higher than that, then I'd have to ask if there is really as much benefit as it seems. If the purpose is ultimately to weed out those who just aren't compatible, it seems a 1 day project would suffice.