If you’re a gmail user, you may have noticed that you can never run out of gmail invites nowadays. You send some off – whoosh, the next day you’re at 50 again.
This basically means that Google wants to spread gmail faster now. The only reason I can think of why they still stick to the invite system is that this may make it harder for robots to sign up (how long until someone automates this??).
What you can do, of course, is send yourself some invites, thus creating a larger space to store stuff.
Or, use it as a better sorting mechanism – instead of applying tags, forward the mail to the account you created for that topic.
As it is possible for anybody to use multiple gmail accounts for him or herself, why doesn’t google just offer bigger accounts?