[code_duck]

Actually, if you went one step beyond and asked for opinions or non-obvious answers to any of those, I'd consider that perfectly suitable for the site.

For example

2. is there an open source implementation of PageRank?

3. any tips on how to fake handwritten Objective C so Apple will accept my app?

4. I wrote my app in BASIC instead of Objective C and Steve Jobs said it was okay

[mkramlich]

here are some more common patterns that HN seems to find acceptable:

1. <something-something-something> Google?

2. <something> Facebook <something> Apple?

3. when will <Apple|Google|Facebook|Amazon> do <my personal whim here>?

:P

[pgbovine]

here's one more to add to your list: if you do an automated text meta-analysis of "Ask HN" titles and see what words/phrases are correlated with more upvotes, then post your analysis on a blog post, i'm sure people would upvote you like crazy ;)