5. A computer implemented method of facilitating the filtering of unsolicited bulk electronic mail (email), comprising: logging a plurality of recipient patterns for known spammers based, at least in part, on a plurality of emails associated with the known spammers, the plurality of emails associated with the known spammers including emails sent by the known spammers; generating or modifying a probabilistic model for predicting whether an unknown sender identity is a spammer based, at least in part, on the logged recipient patterns for the known spammers, wherein the logged recipient patterns for each of the known spammers includes identification of recipients to which the known identified spammer sends emails; wherein the logged recipient patterns for each of the known spammers indicate whether any of the recipients of the emails sent by the corresponding one of the known spammers have mutually exchanged messages with one another; and determining whether a particular sender identity is a spammer based, at least in part, upon applying the probabilistic model to logged recipient patterns for the particular sender identity, wherein the logged recipient patterns for the particular sender identity indicate whether any of the recipients of emails sent by the particular sender identity have mutually exchanged messages with one another; wherein one of the logged recipient patterns for one of the known spammers indicates whether a first one of the recipients of the emails sent by the one of the known spammers previously sent a message to a second one of the recipients of the emails sent by the one of the known spammers, and wherein one of the logged recipient patterns for the particular sender identity indicates whether a first one of the recipients of the emails sent by the particular sender identity previously sent a message to a second one of the recipients of the emails sent by the particular sender identity.
5. A computer implemented method of facilitating the filtering of unsolicited bulk electronic mail (email), comprising: logging a plurality of recipient patterns for known spammers based, at least in part, on a plurality of emails associated with the known spammers, the plurality of emails associated with the known spammers including emails sent by the known spammers; generating or modifying a probabilistic model for predicting whether an unknown sender identity is a spammer based, at least in part, on the logged recipient patterns for the known spammers, wherein the logged recipient patterns for each of the known spammers includes identification of recipients to which the known identified spammer sends emails; wherein the logged recipient patterns for each of the known spammers indicate whether any of the recipients of the emails sent by the corresponding one of the known spammers have mutually exchanged messages with one another; and determining whether a particular sender identity is a spammer based, at least in part, upon applying the probabilistic model to logged recipient patterns for the particular sender identity, wherein the logged recipient patterns for the particular sender identity indicate whether any of the recipients of emails sent by the particular sender identity have mutually exchanged messages with one another; wherein one of the logged recipient patterns for one of the known spammers indicates whether a first one of the recipients of the emails sent by the one of the known spammers previously sent a message to a second one of the recipients of the emails sent by the one of the known spammers, and wherein one of the logged recipient patterns for the particular sender identity indicates whether a first one of the recipients of the emails sent by the particular sender identity previously sent a message to a second one of the recipients of the emails sent by the particular sender identity. 11. The method of claim 5 , further comprising: logging recipient patterns for the particular sender identity based, at least in part, on the emails sent by the particular sender identity.