> Of course, doing this would almost entirely eliminate the economic incentive for companies to bring in foreign workers since they would be free to negotiate better deals once here

This is ignorant ranting at it's worst. Changing companies for H-1B visa holders is one of the easiest operations in otherwise byzantine world of US immigration. The only restrictions are that the new job should be in same or similar area of expertise which is usually not a problem at all (except in case the person is drastically changing career fields) and should pay at least prevalent wages etc. H-1B holders can and do use these opportunities to find better jobs (usually with higher pay) all the time.