The difference between them are following:
Twitter Features:
1. Limited functionality; find people, send brief messages, direct replies
2. Limited to 140 characters per update
3. Not all people find it immediately useful
4. Over-emphasis on follower counts
5. Easily abused for spam and increasing the noise level
6. Relatively smaller installed user base
7. As yet no readily apparent monetization strategy
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Facebook Features:
1. More difficult to navigate and update
2. Requires investment of time to realize sustained benefit
3. Opt in model requires a user to allow others to connect
4. Less immediate responses; unless you stay logged on continually
5. Overhead of mashup and “thick” applications could limit scalability, bloat cost structure