I think too much is if you have to go into debt to do it. My goal is to put nothing on a credit card.
I think "too much" is when you have to sacrifice other important things to pay for the wedding. E.g. for us, we won't give up getting our own rental place (after sharehousing together for years to save money), and paying for me to finish postgrad studies for the sake of the wedding.
I also want to point out that getting an out of town reception venue, or having a Friday/Sunday wedding may not always be possible. Depending on where guests are coming from, that could just mean passing the costs onto guests. If it's too far out of town, guests have to pay for a night's accommodation if the reception ends late. If there are interstate guests, they would need to take a day off work to travel for a Friday wedding, or to get home after a Sunday night wedding. (Some venues in fact charge extra for Sunday weddings due to higher wage costs.)
I think it was also mentioned on the "Things that annoyed you about other people's weddings" thread that a Friday afternoon ceremony followed by dinner reception may be awkward for parents to fit into their schedules, in terms of having to pick up kids from school and/or find daytime babysitters (not easy apparently?!), on top of possibly taking extra time off work.
Though having said that, I'm getting to the point where I realise no matter what you do for your wedding SOMEONE will always find SOMETHING to criticise about it, so just pick what you're happy and comfortable with, then turn a deaf ear to the critics out there!