Yes I agree, my spam box contains dozens of ads for sex aids etc. I rarely use Google except for the odd sending of LARGE files. But having said that, their spam filter does a good job in removing all the trash.
It is used fairly generally, but my two Hotmail accounts get a little (2 or 3 per day). Occasionally a business will sell it's Client Database to a third party. Sometimes it's a function of your name e.g. Whether the address is easy enough for the random addressers to pick up.
I too have recently experienced a phenomenal increase in gmail spam, often from the same source over and over. I get probably 20/day. It's almost like the spam filter is nonexistent. I didn't see any way to complain to them either.
Both people are solicitors. One gets avalanches of spam, the other gets virtually none. Both of them are well-behaved, don't go trawling where they shouldn't, and to all intents and purposes are identical in their email habits.
It's a funny old world, but anyone who believed that Gmail would be spam-free forever was seriously deluding themselves.