Can I have multiple analytics?

Preferably, I’d gladly use Google Analytics for reference, but possible options of WP.com Stats and, say, ShareThis metrics would be welcome. Yet, does it create any conflict?
One question about Akismet: it works under one code on both my older WP.com vestigial, but still active blog and my new blog project. Isn’t it a mistake technically to keep them going this way?