Fear of overselling could kill your company - it puts a brake on everything you do. Even worse, it gives you the perfect excuse not to market your product to the max, and human nature means you'll actually market it close to the minimum.
My philosophy is to ask "will it scale?" for every part of your business. EVERY step - including sales, support and things like invoicing too. This adds surprisingly little overhead, but if Jon Stewart mentions your product on The Daily Show, you'll be popping champagne corks instead of blood vessels.
On the platform side, services like Appengine make this easy. But you need to have plans in place to scale support, sales and everything else.
Rather than asking "will it scale?", I suggest asking "could it scale?". There's no point in doing up-front work to make something scalable if you don't know if it will be needed, but it's also important not to design features that absolutely could not scale under any circumstances. If you can think to yourself "if I need to scale this, I've got a rough idea of how I would do it" you'll probably be fine. And if not... once again, not being able to scale fast enough is a great problem to have (telling an investor "I don't have time to talk to you, our server's can't keep up with all of our new signups" is a great pitch).
My philosophy is to ask "will it scale?" for every part of your business. EVERY step - including sales, support and things like invoicing too. This adds surprisingly little overhead, but if Jon Stewart mentions your product on The Daily Show, you'll be popping champagne corks instead of blood vessels.
On the platform side, services like Appengine make this easy. But you need to have plans in place to scale support, sales and everything else.