I don't know anything about VCs and funding, that being said how are you supposed to get competitive bidding going if you can't shop term sheets, or verbal offers as this article suggests?
What are you supposed to say, "I have a very good feeling VC X might offer me 4, so you are going to have to offer 5." You can't haggle unless you have concrete alternatives to push the price up.
Summary: A deal is only as good as its best alternative. Keep improving your alternatives until you have a signed term sheet. And keep developing your current offers or they will die. Finally, don’t say "shopping around", it puts investors off their stroke.
What are you supposed to say, "I have a very good feeling VC X might offer me 4, so you are going to have to offer 5." You can't haggle unless you have concrete alternatives to push the price up.