Not really. Individuals who can build a company are under no obligation to sell it to anyone placing unreasonable conditions on the sale. If I'm buying your company, I have a concern that you might pull of of the customers back (having started a new company) but the price I'm willing to offer you compensates you for the book of business you are selling to me. That's where non-solicitation clauses come in.

I think the operative principal here is that employees are at a disadvantage w/r to employers. Buyers and sellers are not presumed to be at any disadvantage w/r to each other.