Parties are funny whether it's a "House Party" or not. It's just hard to tell what people will or won't show up for. My DS's birthday for example. Last year we had it at a Bounce place and only 7 kids came...? That really surprised me considering how much kids love to climb and jump on those things. But the year before and this year, we had his party at Chuck E. Cheese. The first one had 25+ kids at it plus the parents and this year's had about 15 (I forget the exact #) kids and at least one parent for each.
I got a House Party (the 2nd one I applied for--My Thai Kitchen--only a couple of neighbors came) in the fall and turned down for several. I would have thought our demographic would have been more appropriate for the ones we didn't get (Fisher Price Infant Toys--my DD was about 9 months old at that time and I have several friends with kids the same age), Perler Beads (craft projects for elementary age kids--my DS's age group) and the Halloween one (I had tons of ideas). We had a Halloween party anyway and more than 20 people were there between family, friends, DS's classmates and their families.
We just got the Digiorno Pizza & Hoops Party. I think we're going to let our DS have another sleepover with the families invited for Pizza and games before at dinnertime. Give the coupons and other stuff, then let his classmates spend the night and watch movies. I spent so much time last time explaining what it was, it just got annoying.
I also did NOT give anyone's email address this time. If my friends want to go on the website and reply, I'll give them the info but I am not sure whether or how much House Party contacts them through those email addresses.
I am still undecided if the free stuff makes it worth the effort. Some of the ones (especially the Fisher Price one) would definitely make it worth the time but not the ones like the My Thai Kitchen. The reusable bags were nice but the coupons weren't all that great ($1 off 2 items--items are pricey and not readily available in our area) and the place mats were paper. Here is the list for the Digiorno

Your FREE party pack will include:
Other than getting the free pizzas for the party...it's kind of so what. I mean it's fun getting free stuff but most of these things I already have. I keep debating whether to continue to apply for parties or not. I have one more outstanding currently and I don't think I want to deal with it. It's the Singer Sewing one but there are alot more restrictions on it dealing with "borrowing" the sewing machine and then maybe getting to purchase it at a discount.
Good Luck!