Purchasing adwords will not get you indexed.
Google are very good at not allowing adword clients to benefit from their relationship in that way.
Only use adwords if you think you can make money from them, and then always be checking to make sure you are in fact making money.
I don't have any proof and no one has ever said, but from an indexing perspective, it would make sense for them to use the adwords listings as a jumping off point to spider sites. I mean, chances are that if you are advertising in adwords, you probably have a page or site that has either not been indexed or has trouble being indexed. What a wealth of unindexed pages G has in adwords! Considering that Google is all about the most indexed pages to best serve the customer, wouldn't you think that they would use every means possible to index all pages?
I have on more than one occassion heard (read) people comment that their site was either not spidered or not spidered very deeply prior to adwords. I know our site was like that. (please note though, they didn't start deeply spidering our site until months after we used adwords) It could be coincidence. But I wouldn't be surprised that in the googlebot's slow time (does it have any?) that it follows random adwords links to see where they lead and what links lay beyond them.
Again, I have never heard anything definitive but it wouldn't surprise me.
