I do like this . I watch for user agents . Once I see googlebot i wrote a script that queries whois . All queries are cached so I don't have to query every time that IP is used . Then I see the netname . If it's GOGL it's google , if it's YAHOO*** or INKT it's yahoo and MSFT or MSHOTM it's microsoft .
Once I confirm the scripts adds an extra variable if bot and it's id and then i use it through out my site .
What do you think of this against IP ranges? Any input is most welcome .